Quantum dots and devices including the same

ABSTRACT

A quantum dot including a core and a shell disposed on the core wherein one of the core and the shell includes a first semiconductor nanocrystal including zinc and sulfur and the other of the core and the shell includes a second semiconductor nanocrystal having a different composition from the first semiconductor nanocrystal, the first semiconductor nanocrystal further includes a metal and a halogen configured to act as a Lewis acid in a halide form, an amount of the metal is greater than or equal to about 10 mole percent (mol %) based on a total number of moles of sulfur, and an amount of the halogen is greater than or equal to about 10 mol % based on a total number of moles of sulfur, a method of producing the same, and a composite and an electronic device including the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of application Ser. No.16/697,650, filed on Nov. 27, 2019, which claims priority to and thebenefit of Korean Patent Application No. 10-2018-0151184 filed in theKorean Intellectual Property Office on Nov. 29, 2018, and all thebenefits accruing therefrom under 35 U.S.C. § 119, the entire contentsof which are incorporated herein by reference.

BACKGROUND 1. Field

Quantum dots and devices including the same are disclosed.

2. Description of the Related Art

Physical characteristics (e.g., energy bandgaps, melting points, etc.)of nanoparticles that are intrinsic characteristics may be controlled bychanging their particle sizes, unlike bulk materials. For example,semiconductor nanocrystals, also referred to as quantum dots, are asemiconductor material having a nano-sized crystal structure. Thequantum dots have a large surface area per unit volume due to very smallparticle sizes and exhibit quantum confinement effects, and thus havedifferent physicochemical characteristics from the characteristics ofthe bulk material having the same composition.

SUMMARY

An embodiment provides a quantum dot (e.g., an environmentally-friendlyquantum dot) having improved photoluminescence characteristics andthermal stability.

An embodiment provides a method of producing the quantum dot.

An embodiment provides a pattern or a composite including the quantumdot.

An embodiment provides an electronic device including the quantum dot.

In an embodiment, a quantum dot includes a core and a shell disposed onthe core,

-   -   wherein one of the core and the shell includes a first        semiconductor nanocrystal including zinc and sulfur and the        other of the core and the shell includes a second semiconductor        nanocrystal having a different composition from the first        semiconductor nanocrystal,    -   the first semiconductor nanocrystal further includes a metal and        a halogen, the metal and the halogen being configured to act as        a Lewis acid in a halide form,    -   an amount of the metal is greater than or equal to about 10 mole        percent (mol %), based on a total number of moles of sulfur, and    -   an amount of the halogen is greater than or equal to about 10        mol %, based on a total number of moles of sulfur.

The first semiconductor nanocrystal may not include selenium.

The first semiconductor nanocrystal may include zinc sulfide.

The second semiconductor nanocrystal may include a Group II-VI compound,a Group III-V compound, a Group IV-VI compound, a Group IV element orcompound, a Group compound, a Group I-II-IV-VI compound, or acombination thereof.

The second semiconductor nanocrystal may include InP, InZnP, ZnSe,ZnTeSe, ZnSeS, or a combination thereof.

The quantum dot may not include cadmium.

The first semiconductor nanocrystal may be present in the core.

The first semiconductor nanocrystal may be present in the shell.

The metal may include aluminum, magnesium, gallium, antimony, titanium,or a combination thereof.

The metal may include aluminum.

The halogen may include chlorine. The halogen may not include fluorine,iodine, bromine, or a combination thereof. The halogen may not includefluorine, iodine, and bromine.

The amount of the metal may be greater than or equal to about 15 mol %,based on a total number of moles of sulfur.

The amount of the metal may be greater than or equal to about 20 mol %,based on a total number of moles of sulfur.

The amount of the halogen may be greater than or equal to about 15 mol%, based on a total number of moles of sulfur.

The amount of the halogen may be greater than or equal to about 25 mol%, based on a total number of moles of sulfur.

The amount of the metal may be greater than or equal to about 6 mol %,based on a total number of moles of zinc.

The amount of the halogen may be greater than or equal to about 8 mol %,based on a total number of moles of zinc.

An X-ray diffraction spectrum of the quantum dot may exhibit a peak ofthe first semiconductor nanocrystal.

An X-ray diffraction spectrum of the quantum dot may not exhibit a peakof the compound composed of the metal and the halogen.

The shell may include a multi-layered shell including two or more layerswherein adjacent layers may have different compositions.

The multi-layered shell may include a first layer disposed directly onthe core, the first layer including a third semiconductor nanocrystal;and a second layer disposed on the first layer, the second layerincluding the first semiconductor nanocrystal.

The third semiconductor nanocrystal may have a different compositionfrom the first semiconductor nanocrystal.

The third semiconductor nanocrystal may include zinc and selenium.

The second layer may be an outermost layer.

The second semiconductor nanocrystal may include indium and phosphorusand a mole ratio of zinc relative to indium may be less than or equal toabout 40:1.

The quantum dot may further include selenium. In an embodiment, thequantum dot may have a mole ratio of sulfur relative to selenium that isless than or equal to about 2:1.

In an embodiment, the quantum dot may have a mole ratio of zinc relativeto selenium and sulfur that is greater than or equal to about 1.1:1.

The quantum dot may further include R₃PO, RCOOH, RCOOCOR, or acombination thereof on a surface of the quantum dot, wherein R is thesame or different and is a substituted or unsubstituted C1 to C40aliphatic hydrocarbon group, a substituted or unsubstituted C6 to C40aromatic hydrocarbon group, or a combination thereof.

In an embodiment, a method of producing the aforementioned quantum dotincludes:

-   -   preparing a zinc precursor not including a halogen;    -   reacting a Lewis base (e.g., R₃P or R₃PO) (wherein, R is a        substituted or unsubstituted C1 to C40 aliphatic hydrocarbon        group, a substituted or unsubstituted C6 to C40 aromatic        hydrocarbon group, or a combination thereof) with sulfur to        prepare a sulfur precursor;    -   reacting a Lewis acid metal halide including the metal with the        Lewis base to obtain an acid base adduct including the metal and        halogen; and    -   optionally, in the presence of the core or a semiconductor        nanocrystal particle including the core, reacting the zinc        precursor and the sulfur precursor in the presence of the acid        base adduct and a zinc halide to form a first semiconductor        nanocrystal including zinc and sulfur and produce the quantum        dot.

The zinc precursor may include a reaction product of a zinc compound andfatty acid.

The Lewis acid metal halide may include aluminum halide, magnesiumhalide, gallium halide, antimony halide, titanium halide, or acombination thereof.

The Lewis base may include R₃P, R₃PO, (wherein, R is a substituted orunsubstituted C1 to C40 aliphatic hydrocarbon group, a substituted orunsubstituted C6 to C40 aromatic hydrocarbon group, or a combinationthereof), or a combination thereof.

A molar amount of the Lewis acid metal halide may be greater than orequal to about 10% and less than or equal to about 100%, based on atotal number of moles of the sulfur precursor.

A molar amount of the zinc halide may be about 10% to about 100%, basedon a total number of moles of the sulfur precursor.

In an embodiment, a quantum dot-polymer composite includes a polymermatrix and the aforementioned quantum dot in the polymer matrix.

The polymer matrix may include a linear polymer, a cross-linked polymer,or a combination thereof.

The polymer matrix may include a binder polymer including a carboxylicacid group.

The binder polymer including the carboxylic acid group may include

-   -   a copolymer of a monomer combination including a first monomer        including the carboxylic acid group and a carbon-carbon double        bond, a second monomer including a carbon-carbon double bond and        a hydrophobic moiety and not including the carboxylic acid group        and optionally a third monomer including a carbon-carbon double        bond and a hydrophilic moiety and not including the carboxylic        acid group;    -   a multiple aromatic ring-containing polymer having a backbone        structure in which two aromatic rings are bound to a quaternary        carbon atom that is a constituent atom of another cyclic moiety        in a main chain of the backbone structure, the multiple aromatic        ring-containing polymer including the carboxylic acid group        (—COOH); or    -   a combination thereof.

The polymer matrix may include a polymerization product of a monomercombination including a thiol compound including at least one thiolgroup at a terminal end of the thiol compound and an ene compoundincluding a carbon-carbon unsaturated bond, a metal oxide particulate,or a combination thereof.

The quantum dot-polymer composite may be in a form of a patterned film.

The quantum dot-polymer composite may be in a form of a film having athickness of 10 micrometers (μm) and an absorption of blue light havinga wavelength of 450 nm of greater than or equal to about 82% when anamount of the quantum dot is less than or equal to about 45 weightpercent, based on a total weight of the quantum dot-polymer composite.

In an embodiment, a display device includes

-   -   a light source and a photoluminescence element,    -   wherein the photoluminescence element includes the        aforementioned quantum dot-polymer composite, and    -   the light source is configured to provide the photoluminescence        element with incident light.

The incident light may have a (luminescence) peak wavelength of about440 nm to about 460 nm.

The photoluminescence element may include a sheet of the quantumdot-polymer composite.

The photoluminescence element may be a stack structure including asubstrate and a light emission layer disposed on the substrate, whereinthe light emission layer may include a pattern of the quantumdot-polymer composite.

The pattern may include at least one repeating section configured toemit light at a predetermined wavelength.

The pattern may include a first repeating section configured to emit afirst light and a second repeating section configured to emit a secondlight having a different center wavelength from the first light.

The quantum dot according to an embodiment may exhibit improvedphotoluminescence characteristics. The quantum dot may exhibit improvedthermal stability. The quantum dot according to an embodiment, whenincluded in a quantum dot-based photoluminescent color filter (QD-CF),may minimize reduction of photoluminescence properties caused by mediummixing various processes in the manufacturing process, or a combinationthereof, and thus may provide a device having improved properties. Thequantum dot according to an embodiment may be applicable to, e.g., usedin, a variety of light emitting devices and may be included in a displaydevice having a excitation light (e.g., blue excitation light) (such asa liquid crystal display, a display device including an (blue lightemitting) OLED as a light source, or a device including aphotoluminescent color filter disposed on the blue light emitting microLED) (e.g., as a photoluminescent color filter element). Such a lightemitting device may be usefully used in a television (TV), a monitor, amobile device, a virtual reality/augmented reality (VR/AR) device, avehicle display, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages and features of this disclosure willbecome more apparent by describing in further detail exemplaryembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a view showing a reaction mechanism in a method of producing aquantum dot according to an embodiment.

FIG. 2 is a schematic view of a cross-section of a device according toan embodiment.

FIG. 3 is a schematic view of a cross-section of a device according toan embodiment.

FIG. 4 is a schematic view of a cross-section of a device according toan embodiment.

FIG. 5 is a schematic view of a pattern forming process using acomposition according to an embodiment.

FIG. 6 is a graph of Photoconversion Efficiency (percent (%)) versusWavelength (nm) showing light conversion efficiency of the quantumdot-polymer composite patterns including the quantum dots produced inExample 2 and Comparative Example 5, respectively.

FIG. 7 shows the results of X-ray diffraction spectroscopy for thequantum dot of Example 1 and the quantum dot of Comparative Example 4.

DETAILED DESCRIPTION

Advantages and characteristics of this disclosure, and a method forachieving the same, will become evident referring to the followingexample embodiments together with the drawings attached hereto. However,the embodiments should not be construed as being limited to theembodiments set forth herein. If not defined otherwise, all terms(including technical and scientific terms) in the specification may bedefined as commonly understood by one skilled in the art. The termsdefined in a generally-used dictionary may not be interpreted ideally orexaggeratedly unless clearly defined. In addition, unless explicitlydescribed to the contrary, the word “comprise” and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof stated elements but not the exclusion of any other elements.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification.

It will be understood that when an element such as a layer, film,region, or substrate is referred to as being “on” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

Further, the singular includes the plural unless mentioned otherwise. Asused herein, “a”, “an,” “the,” and “at least one” do not denote alimitation of quantity, and are intended to include both the singularand plural, unless the context clearly indicates otherwise. For example,“an element” has the same meaning as “at least one element,” unless thecontext clearly indicates otherwise.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers, and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer, or section from another element, component, region, layer, orsection. Thus, “a first element,” “component,” “region,” “layer”, or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. “At least one” isnot to be construed as limiting “a” or “an.” “Or” means “and/or.” Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending on the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±10% or 5% of the stated value.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

As used herein, unless otherwise described, the term “metal” includesmetal elements and semi-metal elements (Si, B, etc.).

As used herein, unless otherwise described, “alkyl” refers to a linearor branched saturated monovalent hydrocarbon group (e.g., methyl, hexyl,etc.).

As used herein, unless otherwise described, “alkenyl” refers to a linearor branched monovalent hydrocarbon group having at least onecarbon-carbon double bond.

As used herein, unless otherwise described, “aryl” refers to amonovalent hydrocarbon group formed by removing one hydrogen atom fromat least one aromatic ring (e.g., phenyl or naphthyl).

As used herein, unless otherwise described, “substituted” refers toreplacement of hydrogen of a compound by a substituent selected from aC1 to C30 alkyl group, a C2 to C30 alkenyl group, a C2 to C30 alkynylgroup, a C6 to C30 aryl group, a C7 to C30 alkylaryl group, a C1 to C30alkoxy group, a C1 to C30 heteroalkyl group, a C3 to C30 heteroalkylarylgroup, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, aC6 to C30 cycloalkynyl group, a C2 to C30 heterocycloalkyl group,halogen (—F, —Cl, —Br or —I), a hydroxy group (—OH), a nitro group(—NO₂), a cyano group (—CN), an amino or amine group (—NRR′ wherein Rand R′ are each independently hydrogen or a C1 to C6 alkyl group), anazido group (—N₃), an amidino group (—C(═NH)NH₂), a hydrazino group(—NHNH₂), a hydrazono group (═N(NH₂)), an aldehyde group (—C(═O)H), acarbamoyl group (—C(O)NH₂), a thiol group (—SH), an ester group(—C(═O)OR, wherein R is a C1 to C6 alkyl group or a C6 to C12 arylgroup), a carboxyl group (—COOH) or a salt thereof (—C(═O)OM, wherein Mis an organic or inorganic cation), a sulfonic acid group (—SO₃H) or asalt thereof (—SO₃M, wherein M is an organic or inorganic cation), aphosphoric acid group (—PO₃H₂) or a salt thereof (—PO₃MH or —PO₃M₂,wherein M is an organic or inorganic cation), and a combination thereof.

As used herein, unless otherwise described, “monovalent hydrocarbongroup” refers to a C1 to C30 alkyl group, a C2 to C30 alkenyl group, aC2 to C30 alkynyl group, a C6 to C30 aryl group, a C7 to C30 alkylarylgroup, a C1 to C30 alkoxy group, a C1 to C30 heteroalkyl group, a C3 toC30 heteroalkylaryl group, a C3 to C30 cycloalkyl group, a C3 to C15cycloalkenyl group, a C6 to C30 cycloalkynyl group, or a C2 to C30heterocycloalkyl group.

As used herein, unless otherwise described, “hetero” refers to inclusionof at least one to three heteroatoms selected from N, O, S, Si, and P.

As used herein, unless otherwise described, “alkylene group” refers to astraight or branched saturated aliphatic hydrocarbon group having atleast two valences and optionally substituted with at least onesubstituent. As used herein, “arylene group” refers to a functionalgroup having at least two valences obtained by removal of at least twohydrogens in at least one aromatic ring, and optionally substituted withat least one substituent.

As used herein, unless otherwise described, “aliphatic” refers to a C1to C30 linear or branched alkyl group, a C2 to C30 linear or branchedalkenyl group, or a C2 to C30 linear or branched alkynyl group.

As used herein, unless otherwise described, “aromatic” refers to a C6 toC30 aryl group or a C2 to C30 heteroaryl group.

As used herein, unless otherwise described, “alicyclic” refers to a C3to C30 cycloalkyl group, a C3 to C30 cycloalkenyl group, or a C3 to C30cycloalkynyl group.

As used herein, unless otherwise described, “(meth)acrylate” refers toacrylate, methacrylate, or a combination thereof. The (meth)acrylate mayinclude a (C1 to 010 alkyl)acrylate, a (C1 to C10 alkyl)methacrylate, ora combination thereof.

As used herein, unless otherwise described, “alkoxy” refers to alkylgroup that is linked via an oxygen (i.e., alkyl-O—), for examplemethoxy, ethoxy, and sec-butyloxy groups.

As used herein, unless otherwise described, “alkynyl” refers to astraight or branched chain, monovalent hydrocarbon group having at leastone carbon-carbon triple bond (e.g., ethynyl).

As used herein, unless otherwise described, “amine or amino group”refers to a group having the general formula —NRR, wherein each R isindependently hydrogen(amino group, when two R are each hydrogen), aC1-C12 alkyl group, a C7-C20 alkylarylene group, a C7-C20 arylalkylenegroup, or a C6-C18 aryl group.

As used herein, unless otherwise described, “arene” refers to ahydrocarbon having an aromatic ring, and includes monocyclic andpolycyclic hydrocarbons wherein the additional ring(s) of the polycyclichydrocarbon may be aromatic or nonaromatic. Specific arenes includebenzene, naphthalene, toluene, and xylene.

As used herein, unless otherwise described, “arylalkyl” refers to asubstituted or unsubstituted aryl group covalently linked to an alkylgroup that is linked to a compound (e.g., a benzyl is a C7 arylalkylgroup).

As used herein, unless otherwise described, “cycloalkenyl” refers to amonovalent hydrocarbon group having one or more rings and one or morecarbon-carbon double bond in the ring, wherein all ring members arecarbon (e.g., cyclopentyl and cyclohexyl).

As used herein, unless otherwise described, “cycloalkyl” refers to amonovalent hydrocarbon group having one or more saturated rings in whichall ring members are carbon (e.g., cyclopentyl and cyclohexyl).

As used herein, unless otherwise described, “cycloalkynyl” refers to astable aliphatic monocyclic or polycyclic group having at least onecarbon-carbon triple bond, wherein all ring members are carbon (e.g.,cyclohexenyl).

As used herein, unless otherwise described, “ester group” refers to agroup of the formula —O(C═O)Rx or a group of the formula —(C═O)ORx. Inan embodiment, Rx may be C1 to C28 aromatic organic group or aliphaticorganic group. An ester group may include a C2 to C30 ester group, andspecifically a C2 to C18 ester group.

As used herein, unless otherwise described, “heteroalkyl” refers toalkyl group that comprises at least one heteroatom covalently bonded toone or more carbon atoms of the alkyl group. Each heteroatom isindependently chosen from nitrogen (N), oxygen (O), sulfur (S), and orphosphorus (P).

As used herein, unless otherwise described, “ketone” refers to a (e.g.,C2 to C30) ketone group, and specifically a (e.g., C2 to C18) ketonegroup. Ketone groups have the indicated number of carbon atoms, with thecarbon of the keto group being included in the numbered carbon atoms.For example, a C2 ketone group is an acetyl group having the formulaCH₃(C═O)—.

As used herein, “Group” refers to a group of Periodic Table.

As used herein, “Group I” refers to Group IA and Group IB, and examplesmay include Li, Na, K, Rb, and Cs, but are not limited thereto.

As used herein, “Group II” refers to Group IIA and Group IIB, andexamples of Group II metal may be Cd, Zn, Hg, and Mg, but are notlimited thereto.

As used herein, “Group III” refers to Group IIIA and Group IIIB, andexamples of Group III metal may be Al, In, Ga, and TI, but are notlimited thereto.

As used herein, “Group IV” refers to Group IVA and Group IVB, andexamples of a Group IV metal may be Si, Ge, and Sn, but are not limitedthereto.

Quantum dots may absorb light from an excitation source, may betransitioned to an energy excitation state, and emit energycorresponding to energy bandgap of the quantum dots. Energy bandgap ofquantum dots may be controlled by adjusting a size and a composition ofnanocrystal. Quantum dots may be employed for, e.g., used in, variousfields such as a display device, an energy device, or a bio luminescencedevice, and the like and may improve color purity. When being appliedto, e.g., used in, an actual device, quantum dots may be provided in aform of being arranged as a pattern, e.g., may be arranged in a pattern,(e.g., photoluminescent color filter), in a form of being dispersed inthe various media (e.g., organic/inorganic polymer, etc.), or acombination thereof.

For a quantum dot having a core-shell structure, a shell surfacepassivation may provide a somewhat increased luminous efficiency.However, quantum dots may have a core including cadmium. Since cadmiumis an environmentally harmful component, quantum dots which may exhibitimproved photoluminescence properties without cadmium are desirable. Forexample, cadmium-free quantum dots in which a shell (e.g., multi-layeredshell of zinc chalcogenide) is disposed on Group III-V compound (e.g.,InP)-based semiconductor nanocrystal core (hereinafter, abbreviated asInP/ZnSeS quantum dots) may improve luminous efficiency. Despite a highinitial efficiency thereof, the InP/ZnSeS quantum dots may suffer adecrease in a luminous efficiency when the InP/ZnSeS quantum dots areprepared in a form that is to be employed in the actual device (e.g., apattern, a polymer composite, or a combination thereof). The presentinventors have found that when InP/ZnSeS quantum dots (e.g., including aphotocurable component) having an initial efficiency of 60% to 90% gothrough a process of mixing with medium (e.g., including photocurablecomponent), a subsequent process (e.g., heat treatment at a hightemperature), or a combination thereof and thereby is formed in aphotoluminescent color filter, a resulting color filter tends to exhibita decreased efficiency in comparison with the initial luminousefficiency of the quantum dots.

Without being bound by a theory, it is believed that such a decrease inthe efficiency indicates insufficient energy segregation between theexcited electrons/holes generated in the core of the quantum dots andthe surfaces of the quantum dots. Accordingly, when damage to theligands on the surfaces of the quantum dots (QDs) by a medium (e.g.,polymer), a heat treatment, or a combination thereof occurs, damagedregions may act as a trap that provides nonradiative recombination.

While it is believed that a sufficient increase in a thickness of theshell (e.g., ZnSe and ZnS) may bring forth, e.g., provide, separationbetween the electron/holes in the quantum dot core and the surface ofthe quantum dot, the increased thickness of the shell layer may alsolead to a sharp increase in a quantum dot weight. For example, a slightincrease in a thickness of an outermost layer (e.g., ZnS layer) of theshell may cause an increase in a total weight of the quantum dot. Theweight increase may result in a substantial reduction of the number ofquantum dots included in a given weight, leading to a decrease of alight absorption. As the photo-luminescent color filter may tend to bedisposed in a front side of the device, the decrease of the lightabsorption may deteriorate a luminous efficiency and may have adverseeffects on color reproducibility of a display device. Therefore, desiredis a technology that can minimize a decrease in the quantum efficiencycaused by contact with a medium, heat treatment, or a combinationthereof while light absorption is maintained at a desired level.

The quantum dot according to an embodiment achieves the aforementionedtechnical object by having the features described below. The quantum dotaccording to an embodiment includes a core and a shell disposed on thecore, wherein one of the core and the shell includes a firstsemiconductor nanocrystal including zinc and sulfur and the otherincludes a second semiconductor nanocrystal having a differentcomposition from the first semiconductor nanocrystal, the firstsemiconductor nanocrystal further includes a metal and a halogen thatare configured to act as a Lewis acid in a halide form, an amount of themetal is greater than or equal to about 10 mol %, for example greaterthan or equal to about 15 mol %, or greater than or equal to about 20mol %, based on a total number of moles of sulfur, and an amount of thehalogen is greater than or equal to about 10 mol %, for example, greaterthan or equal to about 15 mol %, or greater than or equal to about 20mol %, based on a total number of moles of sulfur. Herein mol % means apercentage based on the total number of moles.

In an embodiment, the quantum dot does not include cadmium. In anembodiment, the quantum dot does not include (restricted and/or toxic)heavy metals (e.g., cadmium, lead, mercury, or a combination thereof).

The first semiconductor nanocrystal may include a metal chalcogenideincluding a Group II metal (e.g., zinc). In an embodiment, the metalchalcogenide may include zinc chalcogenide. In an embodiment, the firstsemiconductor nanocrystal does not include selenium. The firstsemiconductor nanocrystal may include zinc sulfide. The firstsemiconductor nanocrystal may include ZnS, ZnSeS, or a combinationthereof.

The second semiconductor nanocrystal may include a Group II-VI compound,a Group III-V compound, a Group IV-VI compound, a Group IV element orcompound, a Group compound, a Group I-II-IV-VI compound, or acombination thereof. In the quantum dots, the second semiconductornanocrystal may be included in the core.

The Group II-VI compound may be a binary element compound of CdSe, CdTe,ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or a combinationthereof; a ternary element compound of CdSeS, CdSeTe, CdSTe, ZnSeS,ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, HgZnS, HgZnSe, HgZnTe, MgZnSe,MgZnS, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, or a combinationthereof; or a quaternary element compound of HgZnTeS, CdZnSeS, CdZnSeTe,CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or acombination thereof, but is not limited thereto.

The Group III-V compound may be a binary element compound of GaN, GaP,GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or a combinationthereof; a ternary element compound of GaNP, GaNAs, GaNSb, GaPAs, GaPSb,AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, or acombination thereof; or a quaternary element compound of GaAlNP,GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs,GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or a combinationthereof, but is not limited thereto. For example, the Group III-Vcompound may further include a Group II metal, like InZnP.

The Group IV-VI compound may be a binary element compound of SnS, SnSe,SnTe, PbS, PbSe, PbTe, or a combination thereof; a ternary elementcompound of SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe,SnPbTe, or a combination thereof; or a quaternary element compound ofSnPbSSe, SnPbSeTe, SnPbSTe, or a combination thereof, but is not limitedthereto.

The Group compound may be CuInSe₂, CuInS₂, CuInGaSe, CuInGaS, or acombination thereof, but is not limited thereto.

The Group compound may be ZnGaS, ZnAlS, ZnInS, ZnGaSe, ZnAlSe, ZnInSe,ZnGaTe, ZnAlTe, ZnInTe, ZnGaO, ZnAlO, ZnInO, HgGaS, HgAlS, HgInS,HgGaSe, HgAlSe, HgInSe, HgGaTe, HgAlTe, HgInTe, MgGaS, MgAlS, MgInS,MgGaSe, MgAlSe, MgInSe, or a combination thereof, but is not limitedthereto.

The Group I-II-IV-VI compound may be CuZnSnSe or CuZnSnS, but is notlimited thereto.

The Group IV element or compound may be a single substance of Si, Ge, ora combination thereof; or a binary element compound of SiC, SiGe, or acombination thereof, but is not limited thereto.

In a quantum dot of an embodiment, the second semiconductor nanocrystalmay include a Group III-V compound. The second semiconductor nanocrystalmay include InP, InZnP, or a combination thereof.

In a quantum dot of an embodiment, the core may include the secondsemiconductor nanocrystal and the shell may include the firstsemiconductor nanocrystal. In a quantum dot of an embodiment, the coremay include the first semiconductor nanocrystal and the shell mayinclude the second semiconductor nanocrystal.

In a quantum dot of an embodiment, the core may include an indiumphosphide compound (e.g., InP or InZnP). In a quantum dot of anembodiment, the shell may include a zinc sulfide compound (e.g., ZnS orZnSeS).

In a quantum dot of an embodiment, the first semiconductor nanocrystal(or the shell including the first semiconductor nanocrystal) may includea metal and a halogen that are configured to act as a Lewis acid in ahalide form (e.g., at increased amount). In the quantum dot, an amountof the metal may be greater than or equal to about 10 mol %, forexample, greater than or equal to about 15 mol %, or greater than orequal to about 20 mol %, based on a total number of moles of sulfur.

An amount of the halogen may be greater than or equal to about 10 mol %,for example, greater than or equal to about 15 mol %, or greater than orequal to about 20 mol %, based on a total number of moles of sulfur.

The X-ray diffraction spectrum of the quantum dot may not exhibit a peakof a compound including the metal and the halogen (e.g., a metal halidecompound consisting of the Lewis metal and the halogen). The X-raydiffraction spectrum of the quantum dot may not exhibit a peak due to apresence of the metal. The X-ray diffraction spectrum of the quantum dotmay not exhibit a peak due to the presence of the halogen. In anembodiment, the metal and the halogen may be present on the surface ofthe first semiconductor nanocrystal. The X-ray diffraction spectrum ofthe quantum dot may exhibit a zinc blend structure.

By the inclusion of the aforementioned amounts of the metal and thehalogen in the first semiconductor nanocrystal or on the surfacethereof, the quantum dot according to an embodiment may exhibit improvedstability (e.g., chemical stability, thermal stability, or a combinationthereof) with a shell that is not thick, and accordingly, the quantumdot may maintain improved photoluminescence characteristics when thequantum dot undergoes a contact with, e.g., contract, the medium, a heattreatment during forming a pattern or a composite, or a combinationthereof and at the same time, the quantum dot may exhibit improvedexcitation light absorption per unit weight. Without being bound by anytheory, for example, it is believed that in case of the quantum dothaving (e.g., a shell of) the first semiconductor nanocrystal includingthe aforementioned amounts of metal and halogen, the metal and thehalogen may further passivate the surface of the quantum dot in additionto (or in exchange for) the organic ligand present on a surface thereof(or by exchanging the same), and such an effect of the passivation mayimprove a chemical stability, electrical stability, or a combinationthereof of the quantum dots. The quantum dots of an embodiment withhaving such enhanced stability may not undergo (or exhibit a limited orsuppressed level of) luminous efficiency deterioration (e.g., when thequantum dots are in contact with a polymer medium and subject toheat-treating), thus a polymer composite or a pattern including the samemay achieve enhanced luminous efficiency. In an embodiment, the metaland the halogen may passivate the outermost layer of the quantum dot (bya Z-type ligand exchange).

The metal may include aluminum, magnesium, gallium, antimony, titanium,or a combination thereof. The metal may include aluminum.

The halogen may include chlorine. In an embodiment, the halogen does notinclude fluorine, iodine, bromine, or a combination thereof. In anembodiment, the halogen does not include fluorine, iodine, and bromine.

In the quantum dot, an amount of the metal may be greater than or equalto about 10 mol %, greater than or equal to about 11 mol %, greater thanor equal to about 12 mol %, greater than or equal to about 13 mol %,greater than or equal to about 14 mol %, greater than or equal to about15 mol %, greater than or equal to about 16 mol %, greater than or equalto about 17 mol %, greater than or equal to about 18 mol %, greater thanor equal to about 19 mol %, greater than or equal to about 20 mol %,greater than or equal to about 21 mol %, greater than or equal to about22 mol %, greater than or equal to about 23 mol %, greater than or equalto about 24 mol %, greater than or equal to about 25 mol %, or greaterthan or equal to about 26 mol %, based on a total number of moles ofsulfur. The amount of the metal may be less than or equal to about 50mol %, for example, less than or equal to about 45 mol %, less than orequal to about 40 mol %, less than or equal to about 35 mol %, or lessthan or equal to about 30 mol %, based on a total number of moles ofsulfur.

In the quantum dot, an amount of the halogen may be greater than orequal to about 10 mol %, greater than or equal to about 11 mol %,greater than or equal to about 12 mol %, greater than or equal to about13 mol %, greater than or equal to about 14 mol %, greater than or equalto about 15 mol %, greater than or equal to about 16 mol %, greater thanor equal to about 17 mol %, greater than or equal to about 18 mol %,greater than or equal to about 19 mol %, greater than or equal to about20 mol %, greater than or equal to about 21 mol %, greater than or equalto about 22 mol %, greater than or equal to about 23 mol %, greater thanor equal to about 24 mol %, greater than or equal to about 25 mol %, orgreater than or equal to about 26 mol %, based on a total number ofmoles of sulfur. The amount of the halogen may be less than or equal toabout 70 mol %, for example, less than or equal to about 65 mol %, lessthan or equal to about 60 mol %, less than or equal to about 55 mol %,or less than or equal to about 50 mol %, based on a total number ofmoles of sulfur.

An amount of the metal may be greater than or equal to about 5 mol %,for example, greater than or equal to about 5.5 mol %, greater than orequal to about 5.6 mol %, greater than or equal to about 5.7 mol %,greater than or equal to about 5.8 mol %, greater than or equal to about5.9 mol %, greater than or equal to about 6.0 mol %, greater than orequal to about 6.1 mol %, greater than or equal to about 6.2 mol %,greater than or equal to about 6.3 mol %, greater than or equal to about6.4 mol %, greater than or equal to about 6.5 mol %, greater than orequal to about 6.6 mol %, greater than or equal to about 6.7 mol %,greater than or equal to about 6.8 mol %, greater than or equal to about6.9 mol %, greater than or equal to about 7 mol %, greater than or equalto about 7.1 mol %, greater than or equal to about 7.2 mol %, greaterthan or equal to about 7.3 mol %, greater than or equal to about 7.4 mol%, greater than or equal to about 7.5 mol %, greater than or equal toabout 7.6 mol %, greater than or equal to about 7.7 mol %, greater thanor equal to about 7.8 mol %, greater than or equal to about 7.9 mol %,or greater than or equal to about 8 mol %, based on a total number ofmoles of zinc. The amount of the metal may be less than or equal toabout 20 mol %, for example, less than or equal to about 15 mol %, lessthan or equal to about 14 mol %, less than or equal to about 13 mol %,less than or equal to about 12 mol %, less than or equal to about 11 mol%, or less than or equal to about 10 mol %, based on a total number ofmoles of zinc.

An amount of the halogen may be greater than or equal to about 8 mol %,for example, greater than or equal to about 8.5 mol %, greater than orequal to about 9 mol %, greater than or equal to about 9.5 mol %,greater than or equal to about 10 mol %, greater than or equal to about10.5 mol %, greater than or equal to about 11 mol %, greater than orequal to about 11.5 mol %, greater than or equal to about 12 mol %,greater than or equal to about 12.5 mol %, greater than or equal toabout 13 mol %, greater than or equal to about 13.5 mol %, or greaterthan or equal to about 14 mol %, based on a total number of moles ofzinc. The amount of the halogen may be less than or equal to about 30mol %, for example less than or equal to about 25 mol %, less than orequal to about 20 mol %, less than or equal to about 19 mol %, less thanor equal to about 18 mol %, or less than or equal to about 17 mol %,based on a total number of moles of zinc.

A quantum dot including a first semiconductor nanocrystal including theaforementioned contents of metal and halogen may be produced by a methodthat will be described below.

The shell may include a multi-layered shell including at least twolayers wherein the adjacent layers may have different compositions. Inan embodiment, the multi-layered shell may have at least two layers, forexample, two, three, four, five, or more layers. The two adjacent layersof the shell may have different compositions. In the multi-layeredshell, each layer may have a composition that varies along the radius.

In an embodiment, the first semiconductor nanocrystal may be included inthe shell, the shell may have a multi-layered shell structure, and themulti-layered shell may include a first layer disposed directly on thecore and including a third semiconductor nanocrystal and a second layerdisposed on (or directly on) the first layer and including the firstsemiconductor nanocrystal.

The third semiconductor nanocrystal may have a different compositionfrom the first semiconductor nanocrystal. The third semiconductornanocrystal may include a Group II-VI compound, a Group III-V compound,a Group IV-VI compound, a Group IV element or compound, a Groupcompound, a Group I-II-IV-VI compound, or a combination thereof. Anexample of each compound is described above.

The third semiconductor nanocrystal may include a zinc chalcogenide. Thethird semiconductor nanocrystal may include ZnSe, ZnSeS, ZnS, or acombination thereof. In an embodiment, the third semiconductornanocrystal does not include sulfur.

The second layer may be the outermost layer. The thickness of the firstlayer may be about 1 monolayer (ML) of the third semiconductornanocrystal, for example, about 2 ML or more, about 3 ML or more, about4 ML or more, or about 5 ML or more and about 10 ML or less, about 9 MLor less, or about 8 ML or less. The thickness of the second layer may beabout 1 monolayer of the first semiconductor nanocrystal, for example,about 2 ML or more, about 3 ML or more, about 4 ML or more, or about 5ML or more and about 10 ML or less about 9 ML or less, about 8 ML orless, about 7 ML or less, about 6 ML or less, about 5 ML or less, orabout 4 ML or less.

The energy bandgap of the third semiconductor nanocrystal may be largerthan the energy bandgap of the material included the core (e.g., secondsemiconductor nanocrystal) and may be less than the energy bandgap ofthe first semiconductor nanocrystal.

In an embodiment, the core may include the second semiconductornanocrystal, the second semiconductor nanocrystal may include indium andindium and phosphorus. In an embodiment, a mole ratio of zinc relativeto indium may be less than or equal to about 40:1, less than or equal toabout 38:1, less than or equal to about 36:1, less than or equal toabout 34:1, or less than or equal to about 33:1. In an embodiment, amole ratio of zinc relative to indium may be greater than or equal toabout 20:1, greater than or equal to about 22:1, greater than or equalto about 24:1, greater than or equal to about 26:1, greater than orequal to about 28:1, greater than or equal to about 30:1, or greaterthan or equal to about 31:1.

The quantum dot may further include selenium (in the core or the shell).In this case, in the quantum dot, a mole ratio of sulfur relative toselenium may be less than or equal to about 2:1. A mole ratio of zincrelative to selenium and sulfur may be greater than or equal to about1.1:1, or greater than or equal to about 1.2:1 and less than or equal toabout 2:1 or less than or equal to about 1.5:1.

The (non-cadmium) quantum dot according to an embodiment may exhibitimproved luminous efficiency due to the aforementioned structure. Forexample, the quantum dot may have a full width at half maximum (FWHM) ofless than or equal to about 45 nm, less than or equal to about 42 nm,less than or equal to about 41 nm, less than or equal to about 40 nm, orless than or equal to about 39 nm. The quantum dot may have a quantumyield of greater than or equal to about 70%, for example, greater thanor equal to about 75%, greater than or equal to about 76%, greater thanor equal to about 77%, greater than or equal to about 78%, or greaterthan or equal to about 79%.

The quantum dot may absorb light (hereinafter, excitation light) in apredetermined wavelength (e.g., such as a wavelength of greater than orequal to about 300 nm, greater than or equal to about 350 nm, greaterthan or equal to about 400 nm, greater than or equal to about 440 nm, orgreater than or equal to about 450 nm and less than or equal to about700 nm, less than or equal to about 600 nm, less than or equal to about500 nm, less than or equal to about 490 nm, less than or equal to about480 nm, less than or equal to about 470 nm, or less than or equal toabout 465 nm, and may emit light in a longer wavelength than thewavelength of the excitation light. A wavelength of the emitted light(e.g., the center wavelength of the maximum peak) may be controlled byadjusting a size and a composition of the quantum dot. The wavelength ofthe emitted light may be in the range of about 500 nm to about 700 nm,for example, about 500 nm to about 560 nm or about 600 to about 650 nm,but is not limited thereto.

The quantum dot may have a particle size (e.g., a particle diameter orin case of a non-spherical shape, an equivalent diameter that iscalculated from a two dimensional image obtained from an electronmicroscopic analysis of a quantum dot) of greater than or equal to about1 nm and less than or equal to about 100 nm.

As used herein, a value regarding the size (e.g., a diameter or thelike) may represent an average value.

The quantum dot may have a size (e.g., an average size) of about 1 nm toabout 50 nm, for example, greater than or equal to about 2 nm, greaterthan or equal to about 3 nm, greater than or equal to about 4 nm,greater than or equal to about 5 nm, greater than or equal to about 6nm, greater than or equal to about 7 nm, greater than or equal to about8 nm, or greater than or equal to about 9 nm and less than or equal toabout 50 nm, less than or equal to about 40 nm, less than or equal toabout 30 nm, less than or equal to about 29 nm, less than or equal toabout 28 nm, less than or equal to about 27 nm, less than or equal toabout 26 nm, less than or equal to about 25 nm, less than or equal toabout 24 nm, less than or equal to about 23 nm, less than or equal toabout 21 nm, less than or equal to about 20 nm, less than or equal toabout 19 nm, less than or equal to about 18 nm, less than or equal toabout 17 nm, less than or equal to about 16 nm, or less than or equal toabout 15 nm. A shape of the quantum dot is not particularly limited. Forexample, the shape of the quantum dot may be a sphere, a polyhedron, apyramid, a multipod, a cube, a rectangular parallelepiped, a nanotube, ananorod, a nanowire, a nanosheet, or a combination thereof, but is notlimited thereto.

The presence and contents of the metal and the halogen included in thequantum dot may be measured by photoelectron spectroscopy (X-rayphotoelectron spectroscopy, XPS), inductively coupled plasma-atomicemission spectroscopy (ICP-AES), ion chromatography, Rutherfordbackscattering spectroscopy (RBS), and time-of-flight secondary ion massspectrometry (TOFSIMS) but are not limited thereto.

The quantum dot may include an organic ligand on its surface. Theorganic ligand may be bound to a surface of the quantum dot. The organicligand may have a hydrophobic moiety. The organic ligand may be bound toa surface of a surface of the quantum dot. The organic ligand mayinclude RCOOH, RSH, RNH₂, R₂NH, R₃N, R₃PO, RH₂P, R₂HP, R₃P, RH₂PO,R₂HPO, ROH, RC(═O)OR, RC(═O)OC(═O)R, RPO(OH)₂, RHPOOH, R₂POOH, or acombination thereof, wherein, each R is independently a C1 to C40substituted or unsubstituted aliphatic hydrocarbon group such as a C3 toC40 alkyl or alkenyl, a C1 to C40 substituted or unsubstituted aromatichydrocarbon group such as a C6 to C40 aryl group, or a combinationthereof. The organic ligand may coordinate with, e.g., be bound to, thesurface of the obtained nanocrystal and may aid with dispersibility ofthe nanocrystal in the solution, affect light emitting and electricalcharacteristics of the quantum dot, or a combination thereof. Examplesof the organic ligand may include methane thiol, ethane thiol, propanethiol, butane thiol, pentane thiol, hexane thiol, octane thiol, dodecanethiol, hexadecane thiol, octadecane thiol, benzyl thiol; methane amine,ethane amine, propane amine, butyl amine, pentyl amine, hexyl amine,octyl amine, dodecyl amine, hexadecyl amine, octadecyl amine, dimethylamine, diethyl amine, dipropyl amine; methanoic acid, ethanoic acid,propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoicacid, octanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoicacid, oleic acid, or benzoic acid; a phosphine such as a substituted orunsubstituted methyl phosphine (e.g., trimethyl phosphine,methyldiphenyl phosphine, etc.), a substituted or unsubstituted ethylphosphine (e.g., triethyl phosphine, ethyldiphenyl phosphine, etc.), asubstituted or unsubstituted propyl phosphine, a substituted orunsubstituted butyl phosphine, a substituted or unsubstituted pentylphosphine, or a substituted or unsubstituted octylphosphine (e.g.,trioctylphosphine (TOP)); a phosphine oxide such as a substituted orunsubstituted methyl phosphine oxide (e.g., trimethyl phosphine oxide,methyldiphenyl phosphine oxide, etc.), a substituted or unsubstitutedethyl phosphine oxide (e.g., triethyl phosphine oxide, ethyldiphenylphosphine oxide, etc.), a substituted or unsubstituted propyl phosphineoxide, a substituted or unsubstituted butyl phosphine oxide, or asubstituted or unsubstituted octyl phosphine oxide (e.g.,trioctylphosphine oxide (TOPO); a diphenyl phosphine compound, atriphenyl phosphine compound, or an oxide compound thereof; phosphonicacid such as a C5 to C20 alkyl phosphonic acid, and the like; a C5 toC20 alkylphosphinic acid such as hexylphosphinic acid, octylphosphinicacid, dodecanephosphinic acid, tetradecanephosphinic acid,hexadecanephosphinic acid, or octadecanephosphinic acid; and the like,but are not limited thereto. One or more organic ligands may be used.

In an embodiment, a method of producing the quantum dot having theaforementioned composition and structure may include

-   -   preparing a zinc precursor not including a halogen;    -   reacting a Lewis base compound (e.g., R₃P or R₃PO (wherein, R is        hydrogen or a substituted or unsubstituted C1 to C40 aliphatic        hydrocarbon group, a substituted or unsubstituted C6 to C40        aromatic hydrocarbon group, or a combination thereof, provided        that at least one of R is alkyl)) with sulfur to prepare a        sulfur precursor;    -   reacting a Lewis acid metal halide including a metal with the        Lewis base to obtain an acid base adduct including the metal and        halogen; and    -   optionally, in the presence of a core or a semiconductor        nanocrystal particle including the core, reacting the zinc        precursor and the sulfur precursor in the presence of the acid        base adduct and a zinc halide to form a first semiconductor        nanocrystal including zinc and sulfur.

When the quantum dot includes the first semiconductor nanocrystal in theshell, the first semiconductor nanocrystal is formed in the presence ofthe core or the core including the semiconductor nanocrystal particle.

The zinc precursor which does not include a halogen may include dimethylzinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinc carbonate,zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc sulfate, ora combination thereof. The zinc precursor may include a reaction productof a zinc compound (e.g., zinc acetate) and a fatty acid (e.g., amonocarboxylic acid having 10 or more carbon atoms such as stearic acid,oleic acid, palmitic acid, lauric acid, etc.). The reaction of the zinccompound and the fatty acid may proceed for a predetermined time at atemperature of greater than or equal to about 120° C. in an organicsolvent.

The sulfur precursor may be obtained by contacting a sulfur compoundwith a compound which may act as a Lewis base (hereinafter, alsoreferred to as Lewis base compound). The Lewis base compound may includeprimary, secondary, or tertiary phosphine or primary, secondary, ortertiary phosphine oxide. The Lewis base compound may include R₃P orR₃PO (wherein, R is hydrogen or a substituted or unsubstituted C1 to C40aliphatic hydrocarbon group, a substituted or unsubstituted C6 to C40aromatic hydrocarbon group, or a combination thereof), or a combinationthereof. Herein, in the above chemical formula, R may include hydrogen,a substituted or unsubstituted C1 to C40 (e.g., C6 or more, C7 or more,C8 or more, C9 or more, or 010 or more and C40 or less, C30 or less, orC25 or less) aliphatic hydrocarbon group (e.g., alkyl, alkenyl,alkynyl), a substituted or unsubstituted C6 to C40 aromatic hydrocarbongroup, or a combination thereof. The sulfur may include elementalsulfur. The contacting may include dispersing, stirring, or acombination thereof. The contacting may be performed at a temperature ofgreater than or equal to about 120° C., greater than or equal to about130° C., greater than or equal to about 140° C., or greater than orequal to about 150° C. and less than or equal to about 340° C., forexample, less than or equal to about 330° C., less than or equal toabout 320° C., less than or equal to about 310° C., less than or equalto about 300° C., less than or equal to about 290° C., less than orequal to about 280° C., less than or equal to about 270° C., less thanor equal to about 260° C., less than or equal to about 250° C., lessthan or equal to about 240° C., less than or equal to about 230° C.,less than or equal to about 220° C., less than or equal to about 210°C., or less than or equal to about 200° C. Examples of the phosphineoxide may include trioctylphosphine oxide, triphenylphosphine oxide,diphenylphosphine oxide, or a combination thereof, but are not limitedthereto. Examples of the phosphine may include trioctylphosphine,diphenylphosphine, or a combination thereof, but are not limitedthereto.

The Lewis acid metal halide includes the aforementioned metal. Thedetails for the metal are as described above. The Lewis acid metalhalide may include aluminum halide, magnesium halide, gallium halide,antimony halide, titanium halide, or a combination thereof.

The Lewis base is a compound capable of providing an electron pair tothe Lewis acid metal halide. In an embodiment, the Lewis base mayinclude the same compound used to form the sulfur precursor. Details forthe Lewis base are the same as those described in connection with theformation of the sulfur precursor. The Lewis base may include R₃P, R₃PO,or a combination thereof (wherein, R is hydrogen, a substituted orunsubstituted C1 to C40 (e.g., C6 or more, C7 or more, C8 or more, C9 ormore, or 010 or more and C40 or less, C30 or less, or C25 or less)aliphatic hydrocarbon group (e.g., alkyl, alkenyl, alkynyl, etc.), asubstituted or unsubstituted C6 to C40 aromatic hydrocarbon group, or acombination thereof).

The Lewis acid metal halide and the Lewis base react to form an acidbase adduct. The reaction condition is not particularly limited and maybe selected appropriately. The reaction temperature may be greater thanor equal to about 30° C., for example, greater than or equal to about40° C., greater than or equal to about 50° C., greater than or equal toabout 60° C., greater than or equal to about 70° C., greater than orequal to about 80° C., greater than or equal to about 90° C., or greaterthan or equal to about 100° C. and less than or equal to about 300° C.,less than or equal to about 200° C., less than or equal to about 150°C., less than or equal to about 140° C., less than or equal to about130° C., less than or equal to about 120° C., or less than or equal toabout 110° C.

The zinc precursor and the sulfur precursor react in the presence ofacid base adduct and a zinc halide in an organic solvent to form thefirst semiconductor nanocrystal.

According to the method of an embodiment, during the synthesis of afirst semiconductor nanocrystal including Zn and S from the Zn precursorand the S precursor, a metal-containing Lewis acid halide and a zinchalide are used together with the zinc precursor. The method may providea ZnS layer (e.g., that provides good passivation on a shell or anoutermost shell or having a defect-free surface). In addition, themethod may make it possible for the first semiconductor nanocrystal toinclude the metal and the halogen in the aforementioned amount relativeto sulfur or zinc.

Without being bound by any theory, a reaction of forming a zinc sulfidein the method according to an embodiment is described with reference toFIG. 1 . The compounds shown in FIG. 1 are exemplified, but the presentinvention is not limited thereto. Without being bound by any theory,according to the reaction mechanism shown in FIG. 1 , it is believedthat the metal halide and zinc halide facilitate the reaction of theaforementioned zinc precursor and sulfur precursor to generate ZnS. Forexample, the Lewis acid metal halide (e.g., aluminum chloride) acts asLewis acid material to withdraw electrons, and contributes to separatingR₃P from S in the sulfur precursor (e.g., R₃P═S). In addition, zinchalide (e.g., ZnCl₂) acts as Lewis acid contributing to separating S andalso is a Zn precursor, so to provide a ZnS coating or particle havingno defects. The ZnS nanocrystal prepared under the condition may includea metal (e.g., Al) and a halogen (e.g., Cl) within the aforementionedranged amounts.

According to the aforementioned method, when the aforementioned reactionis performed under a, e.g., in the, presence of the core (e.g., indiumphosphide-based core) (or particle including the core, for example, aparticle having a core-shell structure, for example, a particle having afirst shell including zinc selenide on the core including indiumphosphide), the core or the like may be prepared according to anysuitable methods which are not particularly limited. The formation of acore (or particle including core) and the formation of ZnS may beperformed in continuous or in stepwise, which is not particularlylimited.

The amount of each compound in the reaction system may be appropriatelyselected taking into consideration the desirable thickness or size ofthe first semiconductor nanocrystal in quantum dots.

The organic solvent used in the method according to an embodiment is notparticularly limited, but may include any suitable organic solvent thatis capable of being used for preparing a zinc sulfide semiconductornanocrystal. Examples of the organic solvent may include a C6 to C22primary amine such as hexadecylamine; a C6 to C22 secondary amine suchas dioctylamine; a C6 to C40 tertiary amine such as trioctylamine; anitrogen-containing heterocyclic compound such as pyridine; a C6 to C40aliphatic hydrocarbon (e.g., alkane, alkene, alkyne, etc.) such ashexadecane, octadecane, octadecene, or squalane; a C6 to C30 aromatichydrocarbon such as phenyldodecane, phenyltetradecane, or phenylhexadecane; a phosphine substituted with a C6 to C22 alkyl group such astrioctylphosphine; a phosphine oxide substituted with a C6 to C22 alkylgroup such as trioctylphosphine oxide; a C12 to C22 aromatic ether suchas phenyl ether, or benzyl ether, or a combination thereof, but are notlimited thereto. The type and the content of the organic solvent may beappropriately selected taking into consideration compounds in thereaction system and amounts of compounds in the reaction system. Theamount of each compound in the reaction system may be also appropriatelyadjusted if desired (e.g., taking into consideration a desired thicknessof ZnS and the precursor(s), and the like), but may be not particularlylimited. According to an embodiment, the amount of zinc halide may begreater than or equal to about 10 mol %, greater than or equal to about20 mol %, greater than or equal to about 30 mol %, or greater than orequal to about mol % and less than or equal to about 100 mol %, lessthan or equal to about 90 mol %, less than or equal to about 80 mol %,or less than or equal to about 70 mol %, based on a total number ofmoles of the sulfur precursor. The amount of the Lewis metal halide usedmay be greater than or equal to about 10 mol %, greater than or equal toabout 20 mol %, greater than or equal to about 30 mol %, or greater thanor equal to about 40 mol % and less than or equal to about 100 mol %,less than or equal to about 90 mol %, less than or equal to about 80 mol%, or less than or equal to about 70 mol %, based on a total number ofmoles of the sulfur precursor.

In the reaction system, the order of injecting the zinc precursor, thesulfur precursor, the acid base adduct, and the zinc halide is notparticularly limited, but may be appropriately selected. In anembodiment, a first layer including the third semiconductor nanocrystalis formed on the core, a sulfur precursor, and a metal halide (e.g.,zinc halide) are injected at a time point of disappearing the non-metalprecursor for forming the first layer, and subsequently, the acid baseadduct may be injected thereto.

The reaction temperature may be greater than or equal to about 250° C.,for example, greater than or equal to about 280° C., or greater than orequal to about 290° C. For example, the reaction temperature may be lessthan or equal to about 350° C., for example, less than or equal to about340° C., or less than or equal to about 330° C. For example, thereaction temperature may be within a range from about 300° C. to about340° C.

A reaction time is not particularly limited, but may be selectedappropriately. For example, the reaction may be performed, for example,for greater than or equal to about 20 minutes, or greater than or equalto about 25 minutes, but is not limited thereto. Each precursor/compoundmay be added in a single step or a plurality of steps. When adding aprecursor or the like stepwise, the reaction may be performed for apredetermined time (e.g., greater than or equal to about 5 minutes,greater than or equal to about 10 minutes, or greater than or equal toabout 15 minutes) in each step. The reaction may be performed under aninert gas atmosphere or air or under vacuum, but is not limited thereto.

The addition of a nonsolvent to the prepared final reaction solution mayallow nanocrystals coordinated with the organic ligands to be separated(e.g., precipitated). The nonsolvent may be a polar solvent that ismiscible with the solvent used in the reaction and nanocrystals are notdispersible therein. The nonsolvent may be selected depending on thesolvent used in the reaction and may be for example, acetone, ethanol,butanol, isopropanol, ethanediol, water, tetrahydrofuran (THF),dimethylsulfoxide (DMSO), diethylether, formaldehyde, acetaldehyde, asolvent having a similar solubility parameter to the foregoing solvents,or a combination thereof. The separation may be performed usingcentrifugation, precipitation, chromatography, or distillation. Theseparated nanocrystals may be added to the washing solvent and thenwashed as desired. The washing solvent is not particularly limited, anda solvent having a solubility parameter similar to that of the ligandmay be used. Examples thereof may include hexane, heptane, octane,chloroform, toluene, and benzene.

The composition according to an embodiment includes the aforementioned(e.g., a plurality of) quantum dot(s); a dispersing agent; and an(organic) solvent. The dispersing agent may include a binder polymerincluding a carboxylic acid group. The composition may further include aphotopolymerizable monomer including a carbon-carbon double bond andoptionally (thermal or photo) initiator.

An amount of the quantum dot in the composition may be appropriatelyadjusted taking into consideration a desirable final use (e.g., colorfilter, etc.). In an embodiment, the content of the quantum dot may begreater than or equal to about 1 weight percent (wt %), for example,greater than or equal to about 2 wt %, greater than or equal to about 3wt %, greater than or equal to about 4 wt %, greater than or equal toabout 5 wt %, greater than or equal to about 6 wt %, greater than orequal to about 7 wt %, greater than or equal to about 8 wt %, greaterthan or equal to about 9 wt %, greater than or equal to about 10 wt %,greater than or equal to about 15 wt %, greater than or equal to about20 wt %, greater than or equal to about 25 wt %, greater than or equalto about 30 wt %, greater than or equal to about 35 wt %, or greaterthan or equal to about 40 wt %, based on a total solids content of thecomposition. The amount of the quantum dot may be less than or equal toabout 70 wt %, for example, less than or equal to about 65 wt %, lessthan or equal to about 60 wt %, less than or equal to about 55 wt %, orless than or equal to about 50 wt %, based on a total solids content ofthe composition.

The composition according to an embodiment may be used to produce aquantum dot-polymer composite pattern. The composition according to anembodiment may be a quantum dot-containing photoresist composition towhich a photolithography method may be applied. The compositionaccording to an embodiment may be an ink composition that may provide apattern by printing (e.g., a droplet discharge method such as inkjetprinting). The composition according to an embodiment does not include aconjugated polymer (except a cardo binder that will be described below).The composition according to an embodiment may include a conjugatedpolymer. Herein, the conjugated polymer refers to a polymer having aconjugated double bond in its main chain, e.g., a main chain of abackbone structure of the polymer (e.g., polyphenylenevinylene, etc.).

In the composition according to an embodiment, a dispersing agent mayensure dispersion of the quantum dot. In an embodiment, the dispersingagent may be a binder polymer. The binder polymer may include acarboxylic acid group. The binder polymer may include a copolymer of amonomer mixture including a first monomer including a carboxylic acidgroup and a carbon-carbon double bond, a second monomer including acarbon-carbon double bond and a hydrophobic moiety and not including acarboxylic acid group, and optionally a third monomer including acarbon-carbon double bond and a hydrophilic moiety and not including acarboxylic acid group;

-   -   a multiple aromatic ring-containing polymer having a backbone        structure in which two aromatic rings are bound to a quaternary        carbon atom that is a constituent atom of another cyclic moiety        in the main chain and including a carboxylic acid group (—COOH)        (hereinafter, a cardo binder); or    -   a combination thereof.

The copolymer includes a first repeating unit derived from the firstmonomer and a second repeating unit derived from the second monomer, andoptionally a third repeating unit derived from the third monomer.

Examples of the first monomer may include carbonic acid vinyl estercompounds such as acrylic acid, methacrylic acid, maleic acid, itaconicacid, fumaric acid, 3-butenoic acid, vinyl acetate, or vinyl benzoate,but are not limited thereto. One or more first monomers may be used.Examples of the second monomer may be an alkenyl aromatic compound suchas styrene, alpha-methyl styrene, vinyl toluene, or vinyl benzyl methylether; an unsaturated carbonic acid ester compound such as methylacrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butylacrylate, butyl methacrylate, benzyl acrylate, benzyl methacrylate,cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, or phenylmethacrylate; an unsaturated carbonic acid amino alkyl ester compoundsuch as 2-amino ethyl acrylate, 2-amino ethyl methacrylate, 2-dimethylamino ethyl acrylate, or 2-dimethyl amino ethyl methacrylate; amaleimide such as N-phenylmaleimide, N-benzylmaleimide,N-alkylmaleimide; an unsaturated carbonic acid glycidyl ester compoundsuch as glycidyl acrylate or glycidyl methacrylate; a vinyl cyanidecompound such as acrylonitrile, methacrylonitrile; or a unsaturatedamide compound such as acryl amide or methacryl amide, but are notlimited thereto. One or more second monomers may be used. Specificexamples of the third monomer may include 2-hydroxy ethyl acrylate,2-hydroxy ethyl methacrylate, 2-hydroxy butyl acrylate, or 2-hydroxybutyl methacrylate, but are not limited thereto. One or more thirdmonomers may be used.

In the carboxylic acid group-containing polymer (also referred to as abinder or a binder polymer), the content of each of the first repeatingunit or the second repeating unit may independently be greater than orequal to about 10 mol %, for example, greater than or equal to about 15mol %, greater than or equal to about 25 mol %, or greater than or equalto about 35 mol %, based on a total number of moles in the carboxylicacid group containing polymer. In the carboxylic acid group containingpolymer, an amount of the first repeating unit or the second repeatingunit may be less than or equal to about 90 mol %, for example, 89 mol %,less than or equal to about 80 mol %, less than or equal to about 70 mol%, less than or equal to about 60 mol %, less than or equal to about 50mol %, less than or equal to about 40 mol %, less than or equal to about35 mol %, or less than or equal to about 25 mol %, based on a totalnumber of moles in the carboxylic acid group containing polymer. In thecarboxylic acid group containing polymer, if present, an amount of thethird repeating unit may be greater than or equal to about 1 mol %, forexample, greater than or equal to about 5 mol %, greater than or equalto about 10 mol %, or greater than or equal to about 15 mol %, based ona total number of moles in the carboxylic acid group containing polymer.In the binder polymer, an amount of the third repeating unit may be lessthan or equal to about 30 mol %, for example, less than or equal toabout 25 mol %, less than or equal to about 20 mol %, less than or equalto about 18 mol %, less than or equal to about 15 mol %, or less than orequal to about 10 mol %, based on a total number of moles in the binderpolymer.

The carboxylic acid group-containing polymer may include a multiplearomatic ring-containing polymer. The multiple aromatic ring-containingpolymer is known as a cardo binder resin and may commercially available.

The carboxylic acid group-containing polymer may have an acid value ofgreater than or equal to about 50 milligrams of potassium hydroxide pergran) (mg KOH/g). For example, the carboxylic acid group containingpolymer may have an acid value of greater than or equal to about 60 mgKOH/g, greater than or equal to about 70 mg KOH/g, greater than or equalto about 80 mg KOH/g, greater than or equal to about 90 mg KOH/g,greater than or equal to about 100 mg KOH/g, greater than or equal toabout 110 mg KOH/g, greater than or equal to about 120 mg KOH/g, greaterthan or equal to about 125 mg KOH/g, or greater than or equal to about130 mg KOH/g. The acid value of the carboxylic acid group-containingpolymer may be for example less than or equal to about 250 mg KOH/g,less than or equal to about for example, 240 mg KOH/g, less than orequal to about 230 mg KOH/g, less than or equal to about 220 mg KOH/g,less than or equal to about 210 mg KOH/g, less than or equal to about200 mg KOH/g, less than or equal to about 190 mg KOH/g, less than orequal to about 180 mg KOH/g, or less than or equal to about 160 mgKOH/g, but is not limited thereto. The binder polymer may have a weightaverage molecular weight of greater than or equal to about 1,000 gramsper mole (g/mol), for example, greater than or equal to about 2,000g/mol, greater than or equal to about 3,000 g/mol, or greater than orequal to about 5,000 g/mol. The binder polymer may have a weight averagemolecular weight of less than or equal to about 100,000 g/mol, forexample less than or equal to about 50,000 g/mol.

In the composition, an amount of the binder polymer may be greater thanor equal to about 0.5 wt %, for example, greater than or equal to about1 wt %, greater than or equal to about 5 wt %, greater than or equal toabout 10 wt %, greater than or equal to about 15 wt %, or greater thanor equal to about 20 wt %, based on a total weight of the composition,but is not limited thereto. The amount of the binder polymer may be lessthan or equal to about 35 wt %, for example less than or equal to about33 wt %, or less than or equal to about 30 wt %, based on a total weightof the composition. Within the ranges, dispersion of the quantum dot maybe ensured. The amount of the binder polymer may be about 0.5 wt % toabout 55 wt %, based on a total weight of solids in the composition.

In the composition, the polymerizable (e.g., photopolymerizable) monomerincluding the carbon-carbon double bond may include a (e.g.,photopolymerizable) acryl-based monomer. The polymerizable monomer maybe a precursor for an insulating polymer. The acryl-based monomer mayinclude alkyl(meth)acrylate, ethylene glycol di(meth)acrylate,triethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate,pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate,dipentaerythritol penta(meth)acrylate, pentaerythritolhexa(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol Aepoxy(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethyleneglycolmonomethylether (meth)acrylate, novolac epoxy (meth)acrylate,diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate,propylene glycol di(meth)acrylate, tris(meth)acryloyloxyethyl phosphate,or a combination thereof.

An amount of the polymerizable monomer may be greater than or equal toabout 0.5 wt %, for example, greater than or equal to about 1 wt % orgreater than or equal to about 2 wt %, based on a total weight of thecomposition. The amount of the photopolymerizable monomer may be lessthan or equal to about 30 wt %, for example, less than or equal to about28 wt %, less than or equal to about 25 wt %, less than or equal toabout 23 wt %, less than or equal to about 20 wt %, less than or equalto about 18 wt %, less than or equal to about 17 wt %, less than orequal to about 16 wt %, or less than or equal to about 15 wt %, based ona total weight of the composition.

The initiator in the composition may be used for polymerization of themonomers. The initiator is a compound accelerating a radical reaction(e.g., radical polymerization of monomer) by producing radical chemicalspecies under a mild condition (e.g., by heat or light). The initiatormay be a thermal initiator or a photoinitiator. The initiator is acompound capable of initiating a radical polymerization of thepolymerizable acrylic monomer, a thiol compound (which will be describedbelow), or a combination thereof by light. The initiator is notparticularly limited. The initiator may be a thermal initiator. Thethermal initiator may include azobisisobutyronitrile, benzoyl peroxide,and the like, but is not limited thereto. The initiator may be aphotoinitiator. The photoinitiator may include a triazine-basedcompound, an acetophenone compound, a benzophenone compound, athioxanthone compound, a benzoin compound, an oxime ester compound, anaminoketone compound, a phosphine or phosphineoxide compound, acarbazole-based compound, a diketone compound, a sulfonium borate-basedcompound, a diazo-based compound, a biimidazole-based compound, or acombination thereof, but is not limited thereto.

In the composition, an amount of the initiator may be appropriatelyadjusted taking into consideration the polymerizable monomers andamounts of the polymerizable monomers. In an embodiment, the initiatormay be used in an amount range of about 0.01 wt % to about 10 wt %,based on a total weight of the composition, but is not limited thereto.

The composition may further include a (multi- or mono-functional) thiolcompound including at least one (e.g., at least two, three, or four)thiol group(s) (for example, at a terminal end of the (multi- ormono-functional) thiol compound), a metal oxide particulate, or acombination thereof.

The metal oxide particulate may include TiO₂, SiO₂, BaTiO₃, Ba₂TiO₄,ZnO, or a combination thereof. In the composition, an amount of themetal oxide particulate may be greater than or equal to about 1 wt % andless than or equal to about 15 wt %, less than or equal to about 10 wt%, or less than or equal to about 5 wt %, based on a total weight ofsolids in the composition. The metal oxide particulate may have anappropriately selected diameter without a particular limit. The diameterof the metal oxide particulate may be greater than or equal to about 100nm, for example, greater than or equal to about 150 nm, or greater thanor equal to about 200 nm and less than or equal to about 1,000 nm orless than or equal to about 800 nm.

The multi-functional thiol compound may include a compound representedby Chemical Formula 1:

wherein, in Chemical Formula 1, R¹ is hydrogen; a substituted orunsubstituted C1 to C30 linear or branched alkyl group; a substituted orunsubstituted C6 to C30 aryl group; a substituted or unsubstituted C3 toC30 heteroaryl group; a substituted or unsubstituted C3 to C30cycloalkyl group; a substituted or unsubstituted C3 to C30heterocycloalkyl group; a C1 to C10 alkoxy group; a hydroxy group; —NH₂;a substituted or unsubstituted C1 to C30 amine group (—NRR′, wherein Rand R′ are independently hydrogen or a C1 to C30 linear or branchedalkyl group provided that both are not simultaneously hydrogen); anisocyanate group; a halogen; —ROR′ (wherein R is a substituted orunsubstituted C1 to C20 alkylene group and R′ is hydrogen or a C1 to C20linear or branched alkyl group); an acyl halide (—RC(═O)X, wherein R isa substituted or unsubstituted alkylene group and X is a halogen);—C(═O)OR′ (wherein R′ is hydrogen or a C1 to C20 linear or branchedalkyl group); —CN; —C(═O)NRR′ (wherein R and R′ are independentlyhydrogen or a C1 to C20 linear or branched alkyl group); or —C(═O)ONRR′(wherein R and R′ are independently hydrogen or a C1 to C20 linear orbranched alkyl group),

-   -   L₁ is a carbon atom, a substituted or unsubstituted C1 to C30        alkylene group, a substituted or unsubstituted C3 to C30        cycloalkylene group, a substituted or unsubstituted C6 to C30        arylene group, a substituted or unsubstituted C3 to C30        heterocycloalkylene group, or a substituted or unsubstituted C3        to C30 heteroarylene group, wherein a methylene moiety (—CH₂—)        of the substituted or unsubstituted C1 to C30 alkylene group may        be replaced by a sulfonyl moiety (—SO₂—), a carbonyl moiety        (CO), an ether moiety (—O—), a sulfide moiety (—S—), a sulfoxide        moiety (—SO—), an ester moiety (—C(═O)O—), an amide moiety        (—C(═O)NR—) (wherein R is hydrogen or a C1 to C10 alkyl group)        or a combination thereof,    -   Y₁ is a single bond; a substituted or unsubstituted C1 to C30        alkylene group; a substituted or unsubstituted C2 to C30        alkenylene group; a C1 to C30 alkylene group or a C2 to C30        alkenylene group wherein a methylene moiety (—CH₂—) is replaced        by a sulfonyl moiety (—S(═O)₂—), a carbonyl moiety (—C(═O)—), an        ether moiety (—O—), a sulfide moiety (—S—), a sulfoxide moiety        (—S(═O)—), an ester moiety (—C(═O)O—), an amide moiety        (—C(═O)NR—) (wherein R is hydrogen or a C1 to C10 linear or        branched alkyl group), an imine moiety (—NR—) (wherein R is        hydrogen or a C1 to C10 linear or branched alkyl group), or a        combination thereof,    -   m is an integer of 1 or greater,    -   k1 is an integer of 0 or 1 or greater, k2 is an integer of 1 or        greater,    -   a sum of m and k2 is an integer of 3 or greater, and    -   when Y₁ is not a single bond, m does not exceed a valence of Y₁,        and a sum of k1 and k2 does not exceed a valence of L₁.

The multi-functional thiol compound may be a dithiol compound, atrithiol compound, tetrathiol compound, or a combination thereof. Forexample, the thiol compound may be glycol di-3-mercaptopropionate,glycol dimercapto acetate, trimethylolpropanetris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis (2-mercaptoacetate),1,6-hexanedithiol, 1,3-propanedithiol, 1,2-ethanedithiol, polyethyleneglycol dithiol including 1 to 10 ethylene glycol repeating units, or acombination thereof.

An amount of the thiol compound may be less than or equal to about 50 wt%, less than or equal to about 45 wt %, less than or equal to about 40wt %, less than or equal to about 35 wt %, less than or equal to about30 wt %, less than or equal to about 25 wt %, less than or equal toabout 20 wt %, less than or equal to about 15 wt %, less than or equalto about 10 wt %, less than or equal to about 9 wt %, less than or equalto about 8 wt %, less than or equal to about 7 wt %, less than or equalto about 6 wt %, or less than or equal to about 5 wt %, based on a totalweight (or total solid content) of the composition. The amount of thethiol compound may be greater than or equal to about 0.1 wt %, forexample, greater than or equal to about 0.5 wt %, greater than or equalto about 1 wt %, greater than or equal to about 5 wt %, greater than orequal to about 10 wt %, greater than or equal to about 15 wt %, greaterthan or equal to about 20 wt %, or greater than or equal to about 25 wt%, based on a total weight (or total solid content) of the composition.

The composition may further include an organic solvent (or a liquidvehicle). The organic solvent is not particularly limited. The organicsolvent and an amount of the organic solvent may be appropriatelydetermined by taking into consideration the above main components (i.e.,the quantum dot, the dispersing agent, the polymerizable monomer, theinitiator, and if used, the thiol compound) and an additive and anamount of the additive which is described below. The composition mayinclude an organic solvent in a residual amount except for a desiredcontent of the (non-volatile) solid. Examples of the organic solvent (orliquid vehicle) may include ethyl 3-ethoxy propionate, ethylene glycolssuch as ethylene glycol, diethylene glycol, or polyethylene glycol;glycolethers such as ethylene glycolmonomethylether, ethyleneglycolmonoethylether, diethylene glycolmonomethylether, ethyleneglycoldiethylether, or diethylene glycoldimethylether; glycoletheracetates such as ethylene glycol acetate, ethylene glycolmonoethyletheracetate, diethylene glycolmonoethylether acetate, or diethyleneglycolmonobutylether acetate; propylene glycol; propylene glycoletherssuch as propylene glycolmonomethylether, propylene glycolmonoethylether,propylene glycolmonopropylether, propylene glycolmonobutylether,propylene glycoldimethylether, dipropylene glycoldimethylether,propylene glycoldiethylether, or dipropylene glycoldiethylether;propylene glycolether acetates such as propylene glycolmonomethyletheracetate, or dipropylene glycolmonoethylether acetate; amides such asN-methylpyrrolidone, dimethyl formamide, or dimethyl acetamide; ketonessuch as methylethylketone (MEK), methylisobutylketone (MIBK), orcyclohexanone; petroleums such as toluene, xylene, or solvent naphtha;esters such as ethyl acetate, butyl acetate, or ethyl lactate; etherssuch as diethyl ether, dipropyl ether, or dibutyl ether; aliphatic,alicyclic, or aromatic hydrocarbons; or a mixture thereof.

If desired, the composition may further include various additives suchas a light diffusing agent, a leveling agent, or a coupling agent inaddition to the aforementioned components. The amount of the additive isnot particularly limited, and may be controlled within an appropriaterange wherein the additive does not cause an adverse effect onpreparation of the composition and production of the quantum dot-polymercomposite and optionally a patterning of the composite.

If used, the additives may be used in an amount of greater than or equalto about 0.1 wt %, for example, greater than or equal to about 0.5 wt %,greater than or equal to about 1 wt %, greater than or equal to about 2wt %, or greater than or equal to about 5 wt %, based on a total weightof the composition, but is not limited thereto. If used, the content ofthe additives may be less than or equal to about 20 wt %, for example,less than or equal to about 19 wt %, less than or equal to about 18 wt%, less than or equal to about 17 wt %, less than or equal to about 16wt %, or less than or equal to about 15 wt %, based on a total weight ofthe composition, but is not limited thereto.

The composition according to an embodiment may be prepared by a methodincluding: preparing quantum dot dispersion including the aforementionedquantum dot, the dispersing agent, and the organic solvent; and mixingthe quantum dot dispersion with the initiator; the polymerizable monomer(e.g., acryl-based monomer); optionally the thiol compound; optionallythe metal oxide particulate, and optionally the additives. Each of theaforementioned components may be mixed sequentially or simultaneously,but mixing orders are not particularly limited.

The composition may provide a quantum dot-polymer composite by a (e.g.,radical) polymerization.

In an embodiment, the quantum dot-polymer composite includes a polymermatrix; and the aforementioned quantum dot dispersed in the polymermatrix. The polymer matrix may include a dispersing agent (e.g., abinder polymer including a carboxylic acid group), a polymerizationproduct (e.g., an insulating polymer) of an ene compound, i.e., apolymerizable monomer having a carbon-carbon double bond (at least one,for example, at least two, at least three, at least four, or at leastfive carbon-carbon double bonds), optionally a polymerization product ofthe polymerizable monomer and a thiol compound including at least onethiol group (e.g., at a terminal end of the thiol compound), preferablya multi-functional thiol compound including at least one, preferably atleast two thiol groups (e.g., at a terminal end of the multi-functionalthiol compound), a metal oxide particulate(s), or a combination thereof.

In an embodiment, the polymer matrix may include a cross-linked polymerand a dispersing agent (e.g., a carboxylic acid group-containing binderpolymer). In an embodiment, the polymer matrix does not include aconjugated polymer (except for a cardo resin). The cross-linked polymermay include a thiolene resin, a cross-linked poly(meth)acrylate, or acombination thereof. In an embodiment, the cross-linked polymer may be apolymerization product of the ene compound (the polymerizable monomer)and, optionally, the multi-functional thiol compound.

The non-cadmium-based quantum dot, the dispersing agent, or the binderpolymer, the polymerizable monomer, and the multi-functional thiolcompound are the same as described above.

The film of the quantum dot-polymer composite or the quantum dot-polymercomposite pattern that will be described below may have for example athickness, less than or equal to about 30 μm, for example less than orequal to about 25 μm, less than or equal to about 20 μm, less than orequal to about 15 μm, less than or equal to about 10 μm, less than orequal to about 8 μm, less than or equal to about 7 μm and greater thanor equal to about 2 μm, for example, greater than or equal to about 3μm, greater than or equal to about 3.5 μm, or greater than or equal toabout 4 μm.

In an embodiment, patterned film includes a repeating section includinga first section configured to emit a first light, wherein the firstsection includes the quantum dot-polymer composite. The repeatingsection may include a second section emitting a second light having adifferent maximum (photoluminescence) peak wavelength from the firstlight, wherein the second section may include a quantum dot-polymercomposite. The quantum dot-polymer composite of the second section mayinclude a second quantum dot configured to emit the second light. Thesecond quantum dot may include the aforementioned quantum dot. The firstlight or the second light may be red light having a maximumphotoluminescence peak wavelength which is present between about 600 nmand about 650 nm (e.g., about 620 nm to about 650 nm) or green lighthaving a maximum photoluminescence peak wavelength which is presentbetween about 500 nm and about 550 nm (e.g., about 510 nm to about 540nm). The patterned film may further include a third section emitting orpassing a third light (e.g., blue light) different from the first lightand the second light. The third light may have a maximum peak wavelengthranging from about 380 nm to about 480 nm.

In an embodiment, a display device includes a light source and aphotoluminescence element, and the photoluminescence element includes asubstrate and an emission layer disposed on the substrate, and theemission layer includes a film or patterned film of the quantumdot-polymer composite. The light source is configured to provide thephotoluminescence element with incident light. The incident light mayhave a (photoluminescence) peak wavelength of greater than or equal toabout 440 nm, for example, greater than or equal to about 450 nm andless than or equal to about 500 nm, for example, less than or equal toabout 480 nm, less than or equal to about 470 nm, or less than or equalto about 460 nm.

In the emission layer (e.g., patterned film of quantum dot-polymercomposite) of the display device according to an embodiment, the firstsection may be a section emitting red light, and the second section maybe a section emitting green light, and the light source may be anelement emitting blue light.

Optical elements (blue light blocking layer or first optical filterwhich will be described below) for blocking (e.g., reflecting orabsorbing) blue light may be disposed on front surfaces (light-emittingsurfaces) of the first section and the second section.

In the aforementioned display device, the light source may include aplurality of light emitting units corresponding to the first section andthe second section, respectively, and the light emitting units mayinclude a first electrode and a second electrode facing each other andan electroluminescence layer disposed between the first electrode andthe second electrode. The electroluminescence layer may include anorganic light emitting material. For example, each light emitting unitof the light source may include an electroluminescent device (e.g., anorganic light emitting diode (OLED)) configured to emit light of apredetermined wavelength (e.g., blue light, green light, or acombination thereof). Structures and materials of the electroluminescentdevice and the organic light emitting diode (OLED) may be selectedappropriately and are not particularly limited. The light sourceincludes an organic light emitting diode (OLED) emitting blue light (andoptionally, green light).

FIGS. 2 and 3 are schematic cross-sectional views of display devicesaccording to embodiments. Referring to FIGS. 2 and 3 , a light sourceincludes an organic light emitting diode (OLED) emitting blue light. Theorganic light emitting diode OLED may include (at least two, forexample, three or more) pixel electrodes 90 a, 90 b, 90 c formed on asubstrate 100, a pixel defining layer 150 a, 150 b formed between theadjacent pixel electrodes 90 a, 90 b, 90 c, an organic light emittinglayer 140 a, 140 b, 140 c formed on the pixel electrodes 90 a, 90 b, 90c, and a common electrode layer 130 formed on the organic light emittinglayer 140 a, 140 b, 140 c.

A thin film transistor and a substrate may be disposed under the organiclight emitting diode (OLED).

The pixel areas of the OLED may be disposed corresponding to the first,second, and third sections that will be described in detail below,respectively.

A stack structure including a quantum dot-polymer composite (e.g., asection including red quantum dot and a section including green quantumdot) pattern and a substrate may be disposed on the light source. Thesections are configured so that blue light emitted from the light sourceis entered thereinto and red light and green light may be emitted,respectively. Blue light emitted from the light source may pass throughthe third section.

The light (e.g., blue light) emitted from the light source may enter thesecond section 21 and the first section 11 of the quantum dot-polymercomposite pattern 170 to emit (e.g., converted) red light R and greenlight G, respectively. The blue light B emitted from the light sourcepasses through or transmits from the third section 31. Over the secondsection emitting red light, the first section emitting green light, or acombination thereof, an optical element 160 may be disposed. The opticalelement may be a blue cut layer which cuts (e.g., reflects or absorbs)blue light and optionally green light, or a first optical filter layer310 (see FIG. 4 ). The blue cut layer 160 may be disposed on the uppersubstrate 240. The blue cut layer 160 may be disposed between the uppersubstrate 240 and the quantum dot-polymer composite pattern and over thefirst section 11 and the second section 21. Details of the blue cutlayer are the same as set forth for the first optical filter layer 310below.

The display device may be obtained by separately fabricating the stackstructure and (e.g., blue light emitting) LED or OLED and thenassembling the same. Alternatively, the display device may be obtainedby forming a quantum dot-polymer composite pattern directly on the LEDor OLED.

The substrate may be a substrate including an insulating material. Thesubstrate may include glass; various polymers such as a polyester (e.g.,polyethylene terephthalate (PET) polyethylene naphthalate (PEN)); apolymethacrylate, or a polyacrylate; a polycarbonate; a polysiloxane(e.g., polydimethylsiloxane (PDMS)); an inorganic material such as Al₂O₃or ZnO; or a combination thereof, but is not limited thereto. Athickness of the substrate may be selected appropriately taking intoconsideration a substrate material but is not particularly limited. Thesubstrate may have flexibility. The substrate may have a transmittanceof greater than or equal to about 50%, greater than or equal to about60%, greater than or equal to about 70%, greater than or equal to about80%, or greater than or equal to about 90% for light emitted from thequantum dot.

A wire layer including a thin film transistor or the like is formed onthe substrate. The wire layer may further include a gate line, a sustainvoltage line, a gate insulating layer, a data line, a source electrode,a drain electrode, a semiconductor, a protective layer, and the like.The detail structure of the wire layer may be verified according to anembodiment. The gate line and the sustain voltage line are electricallyseparated from each other, and the data line is insulated and crossingthe gate line and the sustain voltage line. The gate electrode, thesource electrode, and the drain electrode form a control terminal, aninput terminal, and an output terminal of the thin film transistor,respectively. The drain electrode is electrically connected to the pixelelectrode that will be described below.

The pixel electrode may function as an anode of the display device. Thepixel electrode may be formed of a transparent conductive material suchas indium tin oxide (ITO) or indium zinc oxide (IZO). The pixelelectrode may be formed of a material having a light-blocking propertysuch as gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium(Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium(Pd), or titanium (Ti). The pixel electrode may have a two-layeredstructure in which the transparent conductive material and the materialhaving a light-blocking property are stacked sequentially.

Between two adjacent pixel electrodes, a pixel define layer (PDL)overlapped with a terminal end of the pixel electrode to divide thepixel electrode into a pixel unit. The pixel define layer is aninsulation layer which may electrically block the at least two pixelelectrodes.

The pixel define layer covers a portion of the upper surface of thepixel electrode, and the remaining region of the pixel electrode that isnot covered by the pixel define layer may provide an opening. An organicemission layer that will be described below may be formed on the regiondefined by the opening.

The organic emission layer defines each pixel area by the pixelelectrode and the pixel define layer. In other words, one pixel area maybe defined as an area formed with one organic emission unit layer whichis contacted with one pixel electrode divided by the pixel define layer.

For example, in the display device according to an embodiment, theorganic emission layer may be defined as a first pixel area, a secondpixel area and a third pixel area, and each pixel area is spaced apartfrom each other leaving a predetermined interval by the pixel definelayer.

In an embodiment, the organic emission layer may emit a third lightbelonging to a visible light region or belonging to an ultraviolet (UV)region. That is, each of the first to the third pixel areas of theorganic emission layer may emit a third light. In an embodiment, thethird light may be a light having the highest energy in the visiblelight region, for example, may be blue light. When all pixel areas ofthe organic emission layer are designed to emit the same light, e.g.,the same colored light, each pixel area of the organic emission layermay be formed of the same or similar materials or may show, e.g.,exhibit, the same or similar properties. Thus a process difficulty offorming the organic emission layer may be reduced, e.g., relieved, andthe display device may be applied for, e.g., used in, a largescale/large area process. However, the organic emission layer accordingto an embodiment is not necessarily limited thereto, but the organicemission layer may be designed to emit at least two different lights.

The organic emission layer includes an organic emission unit layer ineach pixel area, and each organic emission unit layer may furtherinclude an auxiliary layer (e.g., hole injection layer (HIL), holetransport layer (HTL), electron transport layer (ETL), etc.) besides theemission layer.

The common electrode may function as a cathode of the display device.The common electrode may be formed of a transparent conductive materialsuch as indium tin oxide (ITO) or indium zinc oxide (IZO). The commonelectrode may be formed on the organic emission layer and may beintegrated therewith.

A planarization layer or a passivation layer may be formed on the commonelectrode. The planarization layer may include a (e.g., transparent)insulating material for ensuring electrical insulation with the commonelectrode.

In an embodiment, the display device may further include a lowersubstrate, a polarizer disposed under the lower substrate, and a liquidcrystal layer disposed between the stack structure and the lowersubstrate, and in the stack structure, the light emission(photoluminescent) layer 230 may be disposed to face the liquid crystallayer. The display device may further include a polarizer between theliquid crystal layer and the light emission (photoluminescent) layer230. The light source may further include LED and if desired, a lightguide panel.

Non-limiting examples of the display device (e.g., a liquid crystaldisplay device) according to an embodiment are illustrated with areference to a drawing. FIG. 4 is a schematic cross sectional viewshowing a liquid crystal display according to an embodiment. The displaydevice of an embodiment may include a liquid crystal panel 200, a lowerpolarizer 300 disposed under the liquid crystal panel 200, and abacklight unit (BLU) disposed under the lower polarizer 300.

The liquid crystal panel 200 includes a lower substrate 210, a stackstructure, and a liquid crystal layer 220 disposed between the stackstructure and the lower substrate. The stack structure includes atransparent substrate (or referred to as an upper substrate) 240 and aphotoluminescent layer 230 including a pattern including a quantumdot-polymer composite.

The lower substrate 210 that is also referred to as an array substratemay be a transparent insulating material substrate. The substrate is thesame as described above. A wire plate 211 is provided on an uppersurface of the lower substrate 210. The wire plate 211 may include aplurality of gate wires (not shown) and data wires (not shown) thatdefine a pixel area, a thin film transistor disposed adjacent to acrossing region of gate wires and data wires, and a pixel electrode foreach pixel area, but is not limited thereto. Details of such a wireplate are not particularly limited.

The liquid crystal layer 220 may be disposed on the wire plate 211. Theliquid crystal layer 220 may include an alignment layer 221 on and underthe liquid crystal layer 220 to initially align the liquid crystalmaterial included therein. Details (e.g., a liquid crystal material, analignment layer material, a method of forming liquid crystal layer, athickness of liquid crystal layer, or the like) of the liquid crystalmaterial and the alignment layer are known and are not particularlylimited.

A lower polarizer 300 is provided under the lower substrate. Materialsand structures of the lower polarizer 300 are known and are notparticularly limited. A backlight unit (e.g., emitting blue light) maybe disposed under the polarizer 300.

An upper optical element or an upper polarizer 300 may be providedbetween the liquid crystal layer 220 and the transparent substrate 240,but is not limited thereto. For example, the upper polarizer may bedisposed between the liquid crystal layer 220 and the photoluminescent230. The upper polarizer may be any suitable polarizer that may be usedin a liquid crystal display device. The upper polarizer may be TAC(triacetyl cellulose) having a thickness of less than or equal to about200 μm, but is not limited thereto. In an embodiment, the upper opticalelement may be a coating that controls a refractive index without apolarization function.

The backlight unit includes a light source 110. The light source mayemit blue light or white light. The light source may include a blue LED,a white LED, a white OLED, or a combination thereof, but is not limitedthereto.

The backlight unit may further include a light guide panel 120. In anembodiment, the backlight unit may be an edge-type lighting. Forexample, the backlight unit may include a reflector, a light guide panelprovided on the reflector and providing a planar light source with theliquid crystal panel 200, at least one optical sheet on the light guidepanel, for example, a diffusion plate, a prism sheet, and the like, or acombination thereof, but is not limited thereto. In an embodiment, thebacklight unit does not include a light guide panel. In an embodiment,the backlight unit may be a direct lighting. For example, the backlightunit may have a reflector, and may have a plurality of fluorescent lampsdisposed on the reflector at regular intervals, or may have an LEDoperating substrate on which a plurality of light emitting diodes may bedisposed, a diffusion plate thereon, and optionally at least one opticalsheet. Details (e.g., each component of a light emitting diode, afluorescent lamp, light guide panel, various optical sheets, and areflector) of such a backlight unit are known and are not particularlylimited.

A black matrix (BM) 241 is provided under the transparent substrate 240and has openings and hides a gate line, a data line, and a thin filmtransistor of the wire plate on the lower substrate. For example, theblack matrix 241 may have a lattice shape. The photoluminescent layer230 is provided in the openings of the black matrix 241 and has aquantum dot-polymer composite pattern including a first section (R)configured to emit a first light (e.g., red light), a second section (G)configured to emit a second light (e.g., green light), and a thirdsection (B) configured to emit/transmit, for example blue light. Ifdesired, the photoluminescent layer may further include at least onefourth section. The fourth section may include a quantum dot that emitslight with a different color from light emitted from the first to thirdsections (e.g., cyan, magenta, and yellow light).

In the photoluminescent layer 230, sections forming a pattern may berepeated corresponding to pixel areas formed on the lower substrate. Atransparent common electrode 231 may be provided on the photoluminescentlayer (e.g., photoluminescent color filter layer).

The third section (B) configured to emit/transmit blue light may be atransparent color filter that does not change a (photo)luminescencespectrum of the light source. In this case, blue light emitted from thebacklight unit may enter in a polarized state and may be emitted throughthe lower polarizer and the liquid crystal layer as is. If desired, thethird section may include a quantum dot emitting blue light.

If desired, the display device may further include a light blockinglayer (blue cut filter) or a first optical filter layer. The blue lightblocking layer may be disposed between bottom surfaces of the firstsection (R) and the second section (G) and the upper substrate 240 or ona top surface of the upper substrate 240. The blue light blocking layermay include a sheet having openings that correspond to a pixel areashowing, e.g., expressing, a blue color (e.g., third section) and may beformed on portions corresponding to the first and second sections. Thefirst optical filter layer may be integrally formed as one bodystructure at the portions except portions overlapped with the thirdsection, but is not limited thereto. At least two first optical filterlayers may be spaced apart and be disposed on each of the positionsoverlapped with the first and the second sections.

In an embodiment, the first optical filter layer may block light havinga portion of a wavelength region in the visible light region andtransmit light having other wavelength regions. For example, the firstoptical filter layer may block blue light and transmit light except bluelight. For example, the first optical filter layer may transmit greenlight, red light, and/or or yellow light that is mixed light thereof.

In an embodiment, the first optical filter layer may substantially blockblue light having a wavelength of less than or equal to about 500 nm andmay transmit light in another visible light wavelength region of greaterthan about 500 nm and less than or equal to about 700 nm.

In an embodiment, the first optical filter layer may have a lighttransmittance of greater than or equal to about 70%, greater than orequal to about 80%, greater than or equal to about 90%, or about 100%with respect to the other visible light of greater than about 500 nm andless than or equal to about 700 nm.

The first optical filter layer may include a polymer thin film includinga dye, a pigment, or a combination thereof that absorbs light having awavelength to be blocked. The first optical filter layer may block 80%or greater, for example, 82% or greater, 90% or greater, or 95% orgreater of blue light having a wavelength of less than or equal to about480 nm and may have a light transmittance of greater than or equal toabout 70%, greater than or equal to about 80%, greater than or equal toabout 90%, or about 100% with respect to other visible light of greaterthan about 500 nm and less than or equal to about 700 nm.

The first optical filter layer may block (e.g., absorb) andsubstantially block blue light having a wavelength of less than or equalto about 500 nm and for example may selectively transmit green light orred light. In this case, at least two first optical filter layers may bespaced apart and disposed on each of the portions overlapped with thefirst and second sections, respectively. For example, a first opticalfilter layer selectively transmitting red light may be disposed on theportion overlapped with the section emitting red light and the firstoptical filter layer selectively transmitting green light may bedisposed on the portion overlapped with the section emitting greenlight, respectively. For example, the first optical filter layer mayinclude a first region, a second region, or a combination thereofwherein the first region blocks (e.g., absorb) blue light and red lightand transmits light having a wavelength of a predetermined range (e.g.,greater than or equal to about 500 nm, greater than or equal to about510 nm, or greater than or equal to about 515 nm and less than or equalto about 550 nm, less than or equal to about 545 nm, less than or equalto about 540 nm, less than or equal to about 535 nm, less than or equalto about 530 nm, less than or equal to about 525 nm, or less than orequal to about 520 nm) and the second region blocks (e.g., absorb) bluelight and green light and transmits light having a wavelength of apredetermined range (e.g., greater than or equal to about 600 nm,greater than or equal to about 610 nm, or greater than or equal to about615 nm and less than or equal to about 650 nm, less than or equal toabout 645 nm, less than or equal to about 640 nm, less than or equal toabout 635 nm, less than or equal to about 630 nm, less than or equal toabout 625 nm, or less than or equal to about 620 nm). The first regionmay be disposed at a place overlapped with the section emitting greenlight and the second region may be disposed at a place overlapped withthe section emitting red light. The first region and the second regionmay be optically isolated. The first optical filter (layer) maycontribute to improving color purity of a display device.

The first optical filter layer may be a reflective filter including aplurality of layers (e.g., inorganic material layers) with differentrefractive index. For example, two layers having different refractiveindex may be alternately stacked with each other, or for example a layerhaving a high refractive index and a layer having a low refractive indexmay be alternately stacked with each other

As refractive index different between the layer having a high refractiveindex and the layer having a low refractive index is higher, the firstoptical filter layer having higher wavelength selectivity may beprovided. A thickness and the number of the stacked layer having a highrefractive index and the layer having a low refractive index may bedetermined according to a refractive index of each layer and a reflectedwavelength, for example, each layer having a high refractive index mayhave a thickness of about 3 nm to about 300 nm, and each layer having alow refractive index may have a thickness of about 3 nm to about 300 nm.

A total thickness of the first optical filter layer may be, for example,from about 3 nm to about 10,000 nm, about 300 nm to about 10,000 nm, orabout 1,000 nm to about 10,000 nm. The high refractive index layers mayhave the same thickness, the same material, or a combination thereof asone another or a different thickness, a different material, or acombination thereof from each other. The low refractive index layers mayhave the same thickness, the same material, or a combination thereof asone another or a different thickness, a different material, or acombination thereof from each other.

The display device may further include a second optical filter layer 311(e.g., a red/green or yellow light recycling layer) disposed between thephotoluminescent layer and the liquid crystal layer (e.g., between aphotoluminescent layer and an upper polarizer) and transmitting at leasta part of the third light and reflecting at least a part of the firstlight and the second light. The second optical filter layer may reflectlight in a wavelength region of greater than about 500 nm. The firstlight may be red light, the second light may be green light, and thethird light may be blue light.

In the display device according to an embodiment, the second opticalfilter layer may be formed as an integrated single layer having anapproximately planar surface.

In an embodiment, the second optical filter layer may include amonolayer having a low refractive index, for example, the second opticalfilter layer may be a transparent thin film having a refractive index ofless than or equal to about 1.4, less than or equal to about 1.3, orless than or equal to about 1.2.

The second optical filter layer having a low refractive index may be,for example, a porous silicon oxide, a porous organic material, a porousorganic/inorganic composite, or a combination thereof.

In an embodiment, the second optical filter layer may include aplurality of layers having different refractive indexes, for example,the second optical filter layer may be formed by alternately stackingtwo layers having different refractive indexes, or for example, thesecond optical filter layer may be formed by alternately stackingmaterial having a high refractive index and material having a lowrefractive index.

The layer having a high refractive index in the second optical filterlayer may include, for example, hafnium oxide, tantalum oxide, titaniumoxide, zirconium oxide, magnesium oxide, cesium oxide, lanthanum oxide,indium oxide, niobium oxide, aluminum oxide, silicon nitride, or acombination thereof. According to an embodiment, the layer having a highrefractive index in the second optical filter layer may include avariety of materials having a higher refractive index than the layerhaving a low refractive index.

The layer having a low refractive index in the second optical filterlayer may include, for example, a silicon oxide. According to anembodiment, the layer having a low refractive index in the secondoptical filter layer may include a variety of materials having a lowerrefractive index than the layer having a high refractive index.

As the refractive index difference between the layer having a highrefractive index and the layer having a low refractive index is thehigher, the second optical filter layer may have the higher wavelengthselectivity.

In the second optical filter layer, each thickness of the layer having ahigh refractive index and the layer having a low refractive index andthe stacked number thereof may be determined depending upon a refractiveindex of each layer and the reflected wavelength, for example, eachlayer having a high refractive index in the second optical filter layermay have a thickness of about 3 nm to about 300 nm, and each layerhaving a low refractive index in the second optical filter layer mayhave a thickness of about 3 nm to about 300 nm. A total thickness of thesecond optical filter layer may be, for example, from about 3 nm toabout 10,000 nm, about 300 nm to about 10,000 nm, or about 1,000 nm toabout 10,000 nm. Each of the layer having a high refractive index andthe layer having a low refractive index in the second optical filterlayer may have the same thickness and materials or different thicknessand materials from each other.

The second optical filter layer may reflect at least a portion of thefirst light (R) and the second light (G) and transmits at least aportion (e.g., whole part) of the third light (B). For example, thesecond optical filter layer 140 may transmit only the third light (B) ina blue light wavelength region of less than or equal to about 500 nm andlight in a wavelength region of greater than about 500 nm, that is,green light (G), yellow light, red light (R), and the like may be notpassed through the second optical filter layer and reflected. Thus, thereflected green light and red light may pass through the first and thesecond sections to be emitted to the outside of the display device.

The second optical filter layer may reflect light in a wavelength regionof greater than about 500 nm in greater than or equal to about 70%,greater than or equal to about 80%, or greater than or equal to about90%, or even about 100%.

Meanwhile, the second optical filter layer may have a transmittance tolight in a wavelength region of less than or equal to about 500 nm of,for example, greater than or equal to about 90%, greater than or equalto about 92%, greater than or equal to about 94%, greater than or equalto about 96%, greater than or equal to about 98%, greater than or equalto about 99%, or even about 100%.

In an embodiment, the aforementioned stack structure may be produced bya method using the photoresist composition. The method may include

-   -   forming a film of the composition on a substrate;    -   exposing a selected region of the film to light (e.g., having a        wavelength of less than or equal to about 400 nm); and    -   developing the exposed film with an alkali developing solution        to obtain a pattern of the quantum dot-polymer composite.

The substrate and the composition are the same as described above.Non-limiting methods of forming the aforementioned pattern areillustrated, referring to FIG. 5 .

The composition is coated to have a predetermined thickness on asubstrate in an appropriate method of spin coating, slit coating, andthe like (S1). The formed film may be, optionally, pre-baked (PRB) (S2).The pre-baking may be performed by selecting an appropriate conditionfrom conditions of a temperature, time, an atmosphere, and the like.

The formed (or optionally pre-baked) film is exposed to light having apredetermined wavelength under a mask having a predetermined pattern(S3). A wavelength and intensity of the light may be selected takinginto consideration the (photo)initiator and amounts of the(photo)initiator, the quantum dots and amounts of the quantum dots, andthe like.

The exposed film is treated with an alkali developing solution (e.g.,dipping or spraying) to dissolve an unexposed region and obtain adesired pattern (S4). The obtained pattern may be, optionally,post-baked (POB) to improve crack resistance and solvent resistance ofthe pattern, for example, at about 150° C. to about 230° C. for apredetermined time (e.g., greater than or equal to about 10 minutes orgreater than or equal to about 20 minutes) (S5).

In an embodiment in which the quantum dot-polymer composite pattern hasa plurality of repeating sections, a quantum dot-polymer compositehaving a desired pattern may be obtained by preparing a plurality ofcompositions including a quantum dot having desired photoluminescenceproperties (a photoluminescence peak wavelength and the like) to formeach repeating section (e.g., a red light emitting quantum dot, a greenlight emitting quantum dot, or optionally, a blue light emitting quantumdot) and an appropriate number of times (e.g., twice or more or threetimes or more) repeating a formation of the above pattern about eachcomposition (S6). For example, the quantum dot-polymer composite mayhave, e.g., be provided in, a pattern including at least two repeatingcolor sections (e.g., RGB sections). The quantum dot-polymer compositepattern may be used as a photoluminescence-type color filter in adisplay device.

In an embodiment, the stack structure may be produced using an inkcomposition. The method may include depositing the same (e.g., toprovide a desirable pattern) on the desirable substrate using anappropriate system (e.g., droplet discharging device such as inkjet ornozzle printing device) and heating the same to remove a solvent and toperform a polymerization. The method may provide a highly precisequantum dot-polymer composite film or pattern in a simple and rapid way.

An embodiment provides an electronic device including the quantum dot.The electronic device may include a light emitting diode (LED), anorganic light emitting diode (OLED), a sensor, a solar cell, an imagingsensor, or a liquid crystal display (LCD), but is not limited thereto

Hereinafter, the embodiments are illustrated in more detail withreference to examples. However, they are exemplary embodiments of thepresent invention, and the present invention is not limited thereto.

EXAMPLES Analysis Methods 1. Quantum Dot (Film) PhotoluminescenceAnalysis

A photoluminescence (PL) spectrum of a produced quantum dot-polymercomposite film at an irradiation wavelength of 450 nanometers (nm) isobtained using an Otsuka QE-2100 spectrometer.

The quantum dot-polymer composite film is obtained by separating quantumdots from the quantum dot dispersion by a non-solvent precipitation andcentrifuge or the like, mixing the separated quantum dots with apredetermined monomer or polymer (e.g., acryl-based polymer, thiolenepolymer, or monomer thereof) to provide a mixture, and applying theobtained mixture on a predetermined substrate to cover a barrier filmand curing the same. Then, the amount of quantum dots used for providinga quantum dot-polymer composite film for measuring a photo-conversionefficiency is adjusted in the predetermined amount (taking intoconsideration a weight of the used polymer) in Examples and ComparativeExamples.

2. X-Ray Photoelectron Spectroscopy (XPS) Analysis

An XPS element analysis is performed using Quantum 2000 made by PhysicalElectronics, Inc. under the conditions of an acceleration voltage: 0.5to kiloelectronvolts (keV), 300 watts (W), and a minimum analysis area:10×10 square micrometers.

3. Inductively Coupled Plasma-Atomic Emission Spectroscopic Analysis(ICP-AES)

The ICP-AES is performed using Shimadzu ICPS-8100.

4. Photo-Conversion Efficiency (Conversion Efficiency, CE)

The photo-conversion efficiency is a ratio of the amount of the lightemitted from the quantum dot-polymer composite film relative to a lightdose which the quantum dot polymer composite film absorbs from theexcitation light. The total light dose (B) of excitation light (i.e.,blue light) is obtained by integrating the luminescent spectrum of theexcitation light, and the PL spectrum of the quantum dot polymercomposite film is measured, so the light dose (A) of light in a green orred wavelength and the light dose (B′) of light in a blue wavelengthemitted from the quantum dot polymer composite film are obtained toprovide a conversion efficiency by the following equation:

A/(B−B′)×100=photo-conversion efficiency (%)

The conversion efficiency as defined above is front photo-conversionefficiency.

5. X-Ray Diffraction (XRD) Analysis

An XRD analysis is performed using a Philips XPert PRO equipment with apower of 3 kilowatts (kW).

Reference Example 1: Preparation of InP Core

Indium acetate and palmitic acid are dissolved in 1-octadecene in a 300milliliter (mL) reaction vessel, and the reactor is heated to 120° C.under vacuum. The atmosphere in the reactor is substituted with nitrogenafter 1 hour. After being heated to a high temperature of about 250° C.,a mixed solution of tris(trimethylsilyl) phosphine (TMS3P) andtrioctylphosphine is rapidly injected and reacted for 20 minutes.Acetone is added into the reaction solution that is rapidly cooled at aroom temperature and centrifuged to provide a precipitate, and theprecipitate is dispersed in toluene or cyclohexane. It is confirmed thatthe InP core has a diameter of about 2 nm. A mole ratio of indiumacetate and TMS3P is adjusted to be about 1.5:1.

Example 1

Se is dispersed in trioctylphosphine (TOP) at 120° C. to prepare aSe/TOP solution. S is dispersed in TOP to prepare a S/TOP solution.Aluminum chloride is dispersed and stirred in TOP at 100° C. to preparean aluminum chloride-TOP adduct (hereinafter, referred to as AlCl₃-TOP).

Zinc acetate and oleic acid are dissolved in trioctylamine in a 300 mLreactor and vacuum-treated at 120° C. for 10 minutes to provide a zincprecursor. The atmosphere in the reactor is substituted with nitrogen(N₂) and heated to 280° C., and then cooled to a predeterminedtemperature after passing a predetermined time.

The InP core obtained from Reference Example 1 and a selenium precursor(i.e., Se/TOP obtained by dispersing Se powder in TOP) are added at apredetermined ratio and heated to a high temperature of greater than orequal to 300° C. and reacted for a predetermined time to provide a ZnSeshell.

When the Se precursor is consumed in the reaction system, S/TOP andZnCl₂ are simultaneously added into the reaction system, and afterpassing the predetermined time, AlCl₃-TOP is subsequently added. Thereaction is performed for a total of 1 hour to provide a ZnS layerincluding zinc sulfide.

The obtained final reaction mixture is cooled to a room temperature.Ethanol is added into the cooled final reaction mixture to prepare aprecipitate. The obtained precipitate is centrifuged to obtain quantumdots, and the obtained quantum dots are dispersed in toluene orchloroform.

In the reaction, a ratio (mole ratio) of amounts of the zinc precursor,the selenium precursor, and the sulfur precursor is about 6:2:1.7. Thezinc precursor is used in about 40 times of the amount of the indiumprecursor used during forming the core.

In the reaction, the amounts of the used ZnCl₂ and AlCl₃ are shown inTable 1.

For the prepared quantum dots, the ratio of S and Al is determined fromICP and XPS analyses, and the ratio of S and Cl is determined from ICPand ion chromatography. Some of the results are shown in Table 1 andTable 2 (ICP data). The mole ratio of the selenium with respect toindium (Se:In) is confirmed to be about 16.1:1.

The obtained quantum dots are performed with an X-ray diffractionanalysis. Referring to FIG. 7 , the obtained quantum dots have a zincblend phase and have no peak caused by aluminum chloride.

Comparative Example 1

Quantum dots are prepared in accordance with the same procedure as inExample 1, except that the adding AlCl₃-TOP is omitted.

In the reaction, the contents of the used ZnCl₂ and AlCl₃-TOP are shownin Table 1.

For the prepared quantum dots, the ratios of S and Al are determinedfrom ICP and XPS analyses, and the ratios of S and Cl are determinedfrom ICP and ion chromatography. The results are shown in Table 1 andTable 2.

Comparative Example 2

Quantum dots are prepared in accordance with the same procedure as inExample 1, except that ZnCl₂ is not used.

In the reaction, the contents of the used ZnCl₂ and AlCl₃ are shown inTable 1.

For the prepared quantum dots, the ratios of S and Al are determinedfrom ICP and XPS analyses, and the ratios of S and Cl are determinedfrom ICP and ion chromatography. The results are shown in Table 1 andTable 2.

Comparative Example 3

Quantum dots are prepared in accordance with the same procedure as inExample 1, except that aluminum hydroxide stearate (Al(OH)₂Str) is usedinstead of AlCl₃-TOP.

In the reaction, the contents of the used ZnCl₂ and (Al(OH)₂Str) areshown in Table 1.

For the prepared quantum dots, the ratios of S and Al are determinedfrom ICP-AES and XPS analyses, and the ratios of S and Cl are determinedfrom ICP-AES and ion chromatography. The results are shown in Table 1and Table 2.

Comparative Example 4

Quantum dots are prepared in accordance with the same procedure as inExample 1, except that ZnCl₂ is not used, and the adding AlCl₃-TOP isomitted.

In the reaction, the contents of the used ZnCl₂ and AlCl₃-TOP are shownin Table 1.

For the prepared quantum dots, the ratios of S and Al are determinedfrom ICP and XPS analyses, and the ratios of S and Cl are determinedfrom ICP and ion chromatography. The results are shown in Table 1 andTable 2.

The obtained quantum dots are performed with an X-ray diffractionanalysis. Referring to FIG. 7 , it is confirmed that the obtainedquantum dots have a zinc blend phase. The mole ratio of the seleniumwith respect to indium (Se:In) is about 1:1.

TABLE 1 Content relative to S Content relative to Zn Additives Al/S ×100% Cl/S × 100% Al/Zn × 100% Cl/Zn × 100% Example 1 ZnCl₂ 0.072AlCl₃-TOP 27% 48% 8.4% 14.9%  millimoles 0.08 mmol (mmol) ComparativeZnCl₂ 0  0% 13%  0% 4.0% Example 1 0.072 mmol Comparative 0 AlCl₃-TOP17% 25% 4.9% 7.2% Example 2 0.08 mmol Comparative ZnCl₂ Al(OH)₂Str 5.1% 8.0%  4.0% 4.3% Example3 0.045 mmol 0.04 mmol Comparative 0 0  0%  0% 0%  0% Example 4 (reference)

From the results of Table 1, it is confirmed that the quantum dotsobtained from Example 1 include aluminum and chlorine in a greatlyincreased amount in ZnS nanocrystal.

TABLE 2 P:In (S + Se):In Zn:In (S + Se):Zn Example 1 0.7:1 25.2:1 32.3:11.28:1 Comparative 0.6:1 25.4:1 31.8:1 1.25:1 Example 1 Comparative0.6:1 26.1:1 31.5:1 1.20:1 Example 2 Comparative 0.7:1 24.1:1 30.0:11.24:1 Example 3 Comparative 8.9:1 31.7:1 15.9:1  0.5:1 Example 4

Experimental Example 1: Preparation of Quantum Dot-Polymer Composite andProduction of Pattern Thereof

(1) Preparation of Quantum Dot-Binder Dispersion

Each quantum dot chloroform dispersion according to Example 1 orComparative Examples 1 to 4 is mixed with a binder (a quaternarycopolymer of methacrylic acid, benzyl methacrylate, hydroxyethylmethacrylate, and styrene, acid value: 130 milligrams of potassiumhydroxide per gram (mg KOH/g), molecular weight: 8,000, methacrylicacid:benzyl methacrylate:hydroxyethyl methacrylate:styrene (moleratio)=61.5:12:16.3:10.2) solution (polypropylene glycol monomethylether acetate (PGMEA) having a concentration of 30 weight percent (wt%)) to prepare a quantum dot-binder dispersion.

(2) Preparation of Photosensitive Composition

The quantum dot binder dispersion is mixed with hexaacrylate having thefollowing structure as a photopolymerizable monomer,glycoldi-3-mercaptopropionate (hereinafter, 2T) as a thiol compound, anoxime ester compound as an initiator, and TiO₂ as a light diffusingagent and PGMEA to prepare a composition.

wherein

The prepared composition includes 43 wt % of the quantum dot, 12.5 wt %of the binder polymer, 23 wt % of 2 T, 12 wt % of the photopolymerizablemonomer, 0.5 wt % of the initiator, and 9 wt % of the light diffusingagent based on a total weight of solids in the composition, and a totalsolids content of the prepared composition is 25 wt %.

(3) Production of Quantum Dot-Polymer Composite Pattern and HeatTreatment

Each photosensitive composition is spin-coated on a glass substrate at150 revolutions per minute (rpm) for 5 seconds to obtain films. Thefilms are pre-baked (PRB) at 100° C. These pre-baked films are exposedto irradiation of light (a wavelength: 365 nm, intensity: 100millijoules (mJ)) for 1 second under a mask having a predeterminedpattern (e.g., a square dot or a stripe pattern), developed in apotassium hydroxide aqueous solution (a concentration: 0.043%) for 50seconds to obtain quantum dot-polymer composite patterns (a thickness:about 6 micrometers (μm)).

The obtained pattern is post-baked (POB) (i.e., heat-treated at 180° C.for 30 minutes) under a nitrogen atmosphere.

For the obtained pattern film, the photo-conversion efficiency after PRBand POB is measured, and the results are shown in Table 3 as therelative efficiency to Comparative Example 4.

TABLE 3 Film characteristics (relative efficiency) PRB POB Example 1113% 111% Comparative Example 1 100% 103% Comparative Example 2 108%104% Comparative Example3 103% 103% Comparative Example 4 (reference)100% 100%

From the results of Table 3, it is confirmed that the quantumdot-polymer composite pattern including quantum dots according toExample 1 have improved photo-conversion efficiency, compared with thequantum dot-polymer composite patterns including quantum dots accordingto Comparative Examples.

Example 2

Quantum dots having a photoluminescence center wavelength of 532 to 542nm are synthesized in accordance with the same procedure as in Example1, except that the core size is controlled by changing a reaction timeof core in Reference Example 1.

A quantum dot-polymer composite pattern is prepared in accordance withthe same procedure as in Experimental Example 1, using quantum dots. Theobtained pattern is measured for a luminous efficiency, and the resultsare shown in FIG. 6 . For the obtained pattern, a process maintenancepercent, which is defined by a POB photo-conversion efficiency relativeto a PRB photo-conversion efficiency, is calculated. The results showthe process maintenance percent of about 96.7%.

Comparative Example 5

Quantum dots having a photoluminescence center wavelength of 532 to 542nm are synthesized in accordance with the same procedure as in Example2, except that the adding AlCl₃-TOP is omitted.

The obtained pattern is measured for a luminous efficiency, and theresults are shown in FIG. 6 . For the obtained pattern, a processmaintenance percent, which is defined by a POB photo-conversionefficiency relative to a PRB photo-conversion efficiency, is calculated.The results show the process maintenance percent of about 93.9%.

From the results of FIG. 6 , it is confirmed that quantum dot-polymercomposite pattern including quantum dots according to Example 2 exhibitsa higher photo-conversion efficiency after POB than in the quantumdot-polymer composite including quantum dots according to ComparativeExample 5. As quantum dots according to Example 2 exhibit an improvedconversion efficiency in the same ZnS thickness, compared with thequantum dots according to Comparative Example 5, the thin thickness ofthe shell (final shell ZnS) may be maintained, contributing to improvedabsorption.

Comparative Example 6

Quantum dots are prepared in accordance with the same procedure as inExample 1, except that AlCl₃-TOP is added in the early stage and theintermediate stage of forming the ZnSe layer. A quantum dot-polymercomposite pattern is prepared with the obtained quantum dots inaccordance with the same procedure as in Experimental Example 1, and therelative photo-conversion efficiency after PRB and POB is measured, andthe results are shown in Table 4.

TABLE 4 Single film characteristics (relative efficiency) Addition ofadditives PRB POB Comparative ZnCl₂ AlCl₃-TOP 91% 92% Example 6 ZnSformation Initial ZnSe step formation step ZnCl₂ AlCl₃-TOP 94% 94% ZnSformation In the middle of step ZnSe formation step

From the results of Comparative Example 6, it is confirmed that addingLewis acid base adduct during the forming ZnSe decreasesphotoluminescence properties of quantum dots.

While this disclosure has been described in connection with what ispresently considered to be practical example embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. On the contrary, it is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A method of producing a quantum dot, comprisingpreparing a zinc precursor not comprising a halogen; reacting a Lewisbase with sulfur to prepare a sulfur precursor; reacting a Lewis acidmetal halide comprising a metal with the Lewis base to obtain an acidbase adduct comprising the metal and halogen; and reacting the zincprecursor and the sulfur precursor in the presence of the acid baseadduct and a zinc halide to form a first semiconductor nanocrystalcomprising zinc and sulfur and produce the quantum dot, wherein thequantum dot comprises a core and a shell disposed on the core, whereinone of the core and the shell comprises the first semiconductornanocrystal comprising zinc and sulfur and the other of the core and theshell comprises a second semiconductor nanocrystal having a differentcomposition from the first semiconductor nanocrystal.
 2. The method ofclaim 1, wherein the zinc precursor comprises a reaction product of azinc compound and a fatty acid.
 3. The method of claim 1, wherein theLewis acid metal halide comprises aluminum halide, magnesium halide,gallium halide, antimony halide, titanium halide, or a combinationthereof, and the Lewis base comprises R₃PO, wherein, R is a substitutedor unsubstituted C1 to C40 aliphatic hydrocarbon group, a substituted orunsubstituted C6 to C40 aromatic hydrocarbon group, or a combinationthereof.
 4. The method of claim 1, wherein an amount of the Lewis acidmetal halide is about 10 mole percent to about 100 mole percent, basedon a total number of moles of the sulfur precursor and an amount of thezinc halide is about mole percent to about 100 mole percent, based on atotal number of moles of the sulfur precursor.
 5. The method of claim 1,wherein the first semiconductor nanocrystal does not comprise selenium.6. The method of claim 1, wherein the first semiconductor nanocrystalcomprises zinc sulfide.
 7. The method of claim 1, wherein the secondsemiconductor nanocrystal comprises a Group II-VI compound, a GroupIII-V compound, a Group IV-VI compound, a Group IV element or compound,a Group compound, a Group I-II-IV-VI compound, or a combination thereof.8. The method of claim 1, wherein the second semiconductor nanocrystalcomprises InP, InZnP, ZnSe, ZnTeSe, ZnSeS, or a combination thereof. 9.The method of claim 1, wherein the quantum dot does not comprisecadmium.
 10. The method of claim 1, wherein the first semiconductornanocrystal is present in the core.
 11. The method of claim 1, whereinthe first semiconductor nanocrystal is present in the shell.
 12. Themethod of claim 11, wherein the shell comprises a multi-layered shellcomprising two or more layers wherein adjacent layers have differentcompositions.
 13. The method of claim 11, wherein the secondsemiconductor nanocrystal comprises indium and phosphorus, and a moleratio of zinc relative to indium is less than or equal to about 40:1.14. The method of claim 1, wherein the quantum dot further comprisesselenium, and a mole ratio of sulfur relative to selenium is less thanor equal to about 2:1.
 15. The method of claim 1, wherein the quantumdot further comprises selenium, and in the quantum dot, a mole ratio ofzinc relative to selenium and sulfur is greater than or equal to about1.1:1.
 16. The method of claim 1, wherein the metal comprises aluminum,magnesium, gallium, antimony, titanium, or a combination thereof. 17.The method of claim 1, wherein the metal comprises aluminum.
 18. Themethod of claim 1, wherein the halogen comprises chlorine and does notcomprise fluorine, iodine, and bromine.
 19. The method of claim 1,wherein the content of the metal is greater than or equal to about 15mole percent, based on the total number of moles of sulfur.
 20. Themethod of claim 1, wherein the content of the halogen is greater than orequal to about 15 mole percent, based on the total number of moles ofsulfur.